The Bellows is fundamental, acoustic shear waves as alchemical acupuncture: Sealing the Top (expand your diaphragm) while Closing the Bottom (raise your anus)

The application of the bellows effect in the spiritual and physical practice of inner alchemy is evident in the practice based on the inscription of the historical relic Jade Pendant Inscription of Circulating Qi (《行氣玉佩銘》, Xing Qi Yu Pei Ming) and the practice of the “spirit mutating into qi” (shen ru qi zhong). The former is an assertive method, whereas the latter is a non-assertive method. In simple terms, the practice based on the Jade Pendant Inscription of Circulating Qi (《行氣玉佩銘》, Xing Qi Yu Pei Ming) is to: breathe in and expand your diaphragm, raise your anus and hold, continue for a while, breathe out and relax. The characteristic of this method is “sealing the top, closing the bottom” (shang feng xia bi). By “sealing the top”, it means to stop breathing through your mouth and nostrils for a while. By “closing the bottom”, it means to raise your anus.

http://www.taichiyuen.org/t5_29_eng.htm

Further corroboration of the key factor of flexing the sphincter - aka "raise your anus."

 In the Ph.d. thesis cited recently - the Quick Fire method is described as used to prepare the Elixir - so just as with cooking you first have a quick fire to get the water boiling. Then the slow fire is the longer process of cooking the elixir.

A bellows (tuo yue) is the fundamental of inner alchemy;

 The Jade pendant inscription gives insight into a Daoist meditation practice form the Warring States Period (475–221 BCE). ... as the Jade Pendant Inscription of Conducting Qi (行氣玉佩銘).

  the “contraction of the anus” (shu le yang guan) often adopted in the practice of inner alchemy, as well as “internal breathing” (nei hu xi) or the “spirit mutating into qi” (shen ru qi zhong) used during the Ming and Qing Dynasties may create the bellows (tuo yue) effect for the evolutionary generation of vital energy (zhen qi).

 Acoustic Shear Waves and Acupuncture

acoustic shear wave (ASW) generated by the mechanical movement of the needle. An acupuncture needle was driven by a piezoelectric transducer at 100 Hz or below, and the ASW in human calf was imaged by magnetic resonance elastography. At the cell level, the ASW activated intracellular Ca²⁺ transients and oscillations in fibroblasts and endothelial, ventricular myocytes and neuronal PC-12 cells along with frequency–amplitude tuning and memory capabilities

  A surprising finding is that the Ca²⁺ oscillation remained at 30 min or even 1.5 h after the needle simulation was turned off (Fig. 3b). The latency and memory effects appeared to be in agreement with the long-lasting healing claimed in traditional acupuncture treatment.

https://link.springer.com/article/10.1007/s00424-011-1017-3

This mechanical wave, being the same as acoustic shear wave will have to travel through its preferred paths by means of wave guiding principle. Thus, the meridians are just the physical waveguides that were worked out by the ancient Chinese experimentally. With this interpretation, the circulation system produces both yin and yang. And acupuncture, although externally applied, is based on these forces. In other words, the ancient Chinese model of acupuncture is mechanistic in nature. To complete the circulation, the qi represents not just the mechanical or acoustic wave but also the activation process of calcium and secretion of endorphin.

So chapter six of the book Taoist Yoga: Alchemy and Immortality explains how the Tao is experienced as the Yuan Qi - the "first half" of alchemy training. But then a person can "fall out of enlightenment" or "fall back into worldliness" - still there can be some stabilization where the "ancestral cavity" of the third eye is permanently opened. And so whether it is psychic (siddhis) or spiritual (yuan qi or shakti) depends on the intensity of the energy developed internally.

So the yin qi does not have any substance and the yin qi is aligned with the yang shen via the left eye - and the heart.  So then even with the eyes open - there can be a Yuan Qi connection via the pineal gland but as psychic energy via the yin qi of the left brain intentions via the yang shen (the physical body).

We create another yang shen via the "yin matter" that is superluminal and therefore golden matter - or virtual information as mass that turns back into yuan jing. So in this sense the pineal gland can be permanently opened but if a person just sees light internally that is still the "relative void" of the yin qi and yang qi.

Only once the internal energy is built up and restored via purification does the yuan qi manifest again as the "absolute void" - seeing light externally. So once the pineal gland is permanently open - this is like a tiny taste of the yuan qi as the yuan qi emanates of the pineal gland via the heart. So then that tiny taste of Yuan Qi can be built upon fairly quickly to increase the body's yuan qi and yuan jing through further meditation.
 
So it's a matter of what level of purification a person wants to maintain  - one of the other posters mentioned this recently. How as a "master" gets older then their abilities decrease. Actually this is based solely on how much healing they are doing and teaching - versus how much energy they are storing up inside their bodies via the Yuan Qi.

So the Yang Shen manifesting STILL has some yin qi blockages within it and so the Yang Shen is then sucked back inside the body - and these "red light" (lower body) yin qi shen blockages are then purified via the Yuan Shen and Yuan Qi into yang qi blue light. So just as Gold is a relativistic quantum phenomenon - the golden light is from the Blue light as a spacetime shift of the future being absorbed.


https://www.academia.edu/36514487/Daoist_Body_in_Internal_Alchemy_Neidan_