Thank you for verifying that his work is genuine.
I shall try to summarize his work, Tao and Longevity, in the space below, along with an analysis to whether it is compatible with the GWV.
Meditation, especially if one has some latent illness, will cause tingling, chills, fever or sensations of heat, congestion, swelling, numbness, itching, etc. The feelings are much stronger when one is in a state of quiet than when one is not. Like the tree that wants to be still when the wind won't stop, one's mind becomes more active when it wants to be quiet.
Firstly, when a person starts to meditate, as a result of the relatively quiet state that arises, he realizes the incessant and chaotic nature of his thoughts as the first effect of meditation. When a glass of water is turbid, no dust is observed in it. But if a clarifying agent is added, the dust can be observed to precipitate to the bottom. The dust was there all the time, and it is only in this quiet state that the presence of dust is discovered.
Secondly, an average person gets sleepy in a quiet condition. If fatigued physically, one should sleep. However, if not one should get up to do a bit of exercise.
I believe this falls in the principle of torpor as an unwholesome state, which is congruent with Buddhist teachings.
In ancient Taoist sutras, the word "ch'i" originally means "no fire". This fire refers to afflictions, sexual desires, lust-filled affections, restling/bustling thoughts and a reckless mind. In absence of this, one will be filled with vitality.
Fire moving restlessly is "secondary fire", while fire in appropriate condition is "ruling fire". "Ruling fire" hence causes kundalini to be induced. Kundalini is the warmth phenomenon, the first stage of catus-kusala-mula.
From what he explains in other texts, proper ch'i movement contributes to a blissfulness of the body, similar to the jhana experience. In this case, he says that when the ch'i reaches appropriate condition, kundalini will hence be induced. GWV says that kundalini (or viriya) arises in deep meditation, so this point is consistent.
Chi flows through a different chi channel every 2 hours (total of 12). There is the Tu Mai (spinal cord), Jen Mai (autonomic nervous system), Tai Mai (kidney nervous system), Yang/Yin Wei (cerebrum, cerebellum, diencephalon), Yang/Yin Chiao (genital nervous system, including prostate and hand/feet nerve functions). Chong mai is non-fixed and starts between reproductive organs through the stomach, heart and to the center of the head.
In yoga, there are 3 chi routes (left, middle, right) and 7 chakras (major nerve plexuses in body). In Taoism, there is front, middle and back routes. There are 3 storages for chi, known as upper/middle/lower Tan Tien.
Please note that the words in brackets mean correspondences, not synonyms.
I am not sure if GWV agrees with this esoteric point of view, with the existence of a central channel. I do remember Jhanananda saying that he does not agree with the "microcosmic orbit" of Taoism as there is no circulation sensation going on.
In meditation, blood circulation decreases, endocrine secretion evenly distributes and creates the feeling of being "full" of chi. One can feel tightness in the central nervous system.
When chi starts to move, people erroneously ”concentrate", causing nerves to tighten and hence fall into a state of mental/physical sickness. Meditation does not make a man crazy, but misunderstanding brought about by ignorance of basic principles of meditation can cause abnormal mental states.
I think this brings up the GWV point where meditation does not “cause” mental problems, but reveals them as a spiritual crisis.
Those who employ Buddhist meditation methods generally suppose mental cultivation is sufficient. As a consequence, physical transformations and bodily changes are erroneously ignored.
I think this point itself negates what a lot of meditation teachers say about meditation is just "keeping mental calm", which is not. This point highlights that meditation is a rehabilitation that can involve the body itself.
Without an unwholesome mindstate, one attains mental quietude and kundalini/shakti/real chi/spirit force/spirit heat is generated.
The chi reaction inside the body is not merely connected with breath. There are 3 forms: (1) Wind (normal respiratory system), (2) Chi (Light, easy and slow breath) and (3) Xi (Breath is so slight it almost stops, with energy within the lower abdomen).
Meditation does not cause any of these effects, but merely reveals latent illnesses. However, one cannot avoid the effects of this relationship. One must depend on the body in order to break the shell of its bondage. Everyone will not experience all the phenomena described as it depends on the person's sex, age, and individual mental/physiological state.
First reaction at starting meditation is numbness or swelling of legs.
Second reaction will be at the swollen filling sensation in the back/kidneys/genitals.One should refrain from sexual desires to remedy this. A proverb says: "One starts to think about sex when one is warm and full of food."
Third reaction will be heaviness/aching in the back/shoulder regions. One has to release the mind and forget the body. If equanimous, suddenly, the mind and body will be at ease/loose from the tension and there will be brightness of mind and spirit. The back suddenly straightens and he will be so charged that he cannot fall asleep easily. In this case, let nature take its course.
Fourth reaction will be the possibility of heavy lethargy forcing one to doze. Dreamlike state surfaces. Images and feelings match subconscious functions, giving rise to mental states, thoughts and concepts (States of Mara). Going through this depends on one's wisdom, thought, personality, psychological propensities and physiological condition. After the fourth, one will feel more awake. Points of lights can appear in front of your eyes, in different shapes and colors.
Fifth reaction will be joyfulness. There might be wonderful inner sounds or even ringing noises. This is caused by trembling chi generating brainwave activities. However, one may hear voices - this is a mixture of what has been seen, heard, thoughts and known before. This requires a strong mind. Guiding the chi down, the stage is passed.
Sixth reaction is a swelling in both temples and another desire to doze. Open/closed eyes will see lights like the sun/moon/fluorescence. There might be observations of people/events happening inside this light (premonitive vision). This is due to fluctuations of chi in the brain that induces thoughts or images. However, if the chi is not adjusted suitably, there might be nasal dripping. If one passes this stage, there might be presence of fragrances.
Seventh reaction will be chi at the nose. Some people will have pain/heavy sensations at the crown, as if pressed upon. Diverting attention and letting it be natural, a comfortable and refreshing feeling will move downward from the top of the head (Ching An). Thoughts and illusions weakened, one naturally straightens posture and experiences the first step of "samadhi". Sweet, cool saliva can descend. There might be very little hunger. There can be sounds like "pi pi" in the head.
I find that I experienced the third reaction, where I would have a bolting of the body and then have a moment where I cannot fall asleep easily.
I also find that he seems to have described the spiritual crisis in the fourth reaction.
The fifth reaction is obviously talking about the charisms. Ringing noises point to the auditory charism.
The sixth reaction is something I've experienced too, where there are lights or fluorescences. Probably the visual charism in this case.
The seventh reaction is obviously a deep state of meditation. I remember that Jhanananda described an energetic movement from crown-down, so I believe that this particular point corresponds to it?
He elaborates that the above 7 reactions are signs of the opening of the "back channel", and that there are also other signs for the "front channel", which he says is much more difficult to open. He continues below:
First reaction is chi vibrating in intestines/stomach. There may be hiccoughs, yawning, farting and serious diarrhea. It can feel as if something is blocked in the chest and he wishes to vomit out but cannot. It might be possible to vomit out a dense, dark-grey phlegm. This can lead to opening of the throat chakra. Sexual intercourse should be avoided at this stage, especially for cultivators who want a faster result. After this stage, one will enter the next stage.
Second reaction is that the chest feels opened and broadened. Sometimes, there are crackling noises around the heart or curling up of the tongue and feeling of sinking down. External breathing stops. The tongue curls back to the uvula. There might be sounds of birds. There will be golden light appearing in front of the eyes. There is slight breathing in the abdomen.
Third reaction is the external and inner breath stopping completely. Genitals might retract tightly.
I cannot relate completely to the second or third reactions... but I have felt the chest congestion, which is said to be the heart chakra being closed.
When front and back channels are completely open, chi goes to the legs and feet and causes a "non-sexual orgasm". After a while, chi ascends to front of head, then descends to fill the entire body. A person feels as if his body does not exist.
One feels while walking as if he is walking in the sky, or perhaps that he is treading on a sponge.
Apparently the above is the sign that the Tu and Jen (front and back) channels are open, in Taoist terms. He says that when these channels open, the channels referred to by yoga as the left and right channels naturally open up as well. He says that at this stage one begins to cultivate wisdom and moves beyond the practice of meditation technique, which deals with the opening of the central channel.
I do not think that I have experienced the above, so I cannot comment. I am not sure of the GWV's perspective on this, perhaps it can be verified?
After opening both channels, the body feels light, clear, warm and soft. One will introspect and recognize the illumination of the origin of nature and life. One can separate from and unite with the "later heaven body". This allows for the solid foundation for Tao cultivation, as one has claimed the initial fruit.
I think "later heaven body" refers to the out-of-body experience as a result of deep meditation. As GWV says, this is a fruit of attainment, which is consistent.
"The stars of the universe stop wheeling, the sun and moon are united."
Very few can achieve genuine rotation of the river chariot and circulate chi among the eight extra meridians. Even fewer understand the stage of separation and unification of body, mind and the origin of Nature. Therefore, even if one sincerely wants to teach this, a student with the ability to receive this supreme instruction is rare. After this stage, a person goes beyond earthly things and enters into the metaphysical realm. Even if a teacher wished to describe this in detail, a student with the wisdom and experience to receive these instructions beyond the realm of the human world would be exceptional.
This is exactly where I see the huge similarity between GWV and Nan Huai Chin. Jhanananda talked about his separation of body, as well as the experience of the immaterial realm, which seems to be exactly what Huai Chin is talking about here. I did not understand this passage when I first read it, until I've read GWV's take on it, and everything clicked.
There are a few more pages, but when I get more time I will post it up. I would love to know the GWV's take on the information.