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The sun rises from Fusang in the east of the sea; the operation of Huohou (Fire Timing) flies across like a fire wheel, and one must not slacken in effort.
Just as a deer cart carries the substance up to the top of Kunlun, Mugong (Wood-Mercury, referring to Liver-Hun/Spiritual Qi) naturally returns to the Shenshi (Divine Chamber, referring to Dantian/Mind Residence).
The red sun of Fusang moves from west to east. The Zhengyao (Correct Medicine, referring to Primordial Qi) shines brightly like the red sun, coming from the east to the west. At this time, one must hastily drive the fire wheel, flying across the vast ocean of waves, ascending from the Weilu point (Tailbone) through the Jiaji Double Pass.
Chunyangzi said: "Sit with regulated breath between Zi hour and Wu hour, passing through the Jiaji Double Pass to reach Kunlun." He also said: "Observe between Zi after and Wu before; a vein of Tianjin (Heavenly Saliva/Qi Fluid) is at the end of the spine." Xiao Zixu said: "Several times smilingly pointing to the road to Kunlun, there is clearly a path through the Jiaji." However, on the left side of the reverse path, without the Deer Cart, one cannot push or pull. The Deer Cart refers to Zhenyi (True Intention/Focused Will); with this True Intention, one can cross dangers, pass the Double Pass, ascend to Kunlun, descend to the Queqiao (Magpie Bridge), and allow the Huo Gong (Living Mercury/Dynamic Spirit) to enter the Jinding Shenshi (Golden Cauldron Divine Chamber), thereby becoming an eternal treasure of the body.

The Gen Nan (Gen Male, metaphor for the medicine originating from the Gen Palace) first returns to the Hundun Wo (Chaos Nest, i.e., Zuqi Acupoint). The husband and wife thus tie their silk ropes (Yin-Yang union).
Keep the Six Gates (sensory openings such as eyes, ears, nose, mouth) tightly closed and diligently add fire; the spring light within the tent must maintain Taihe (Great Harmony).
Gen Nan metaphorically represents the medicine coming from the Gen Palace. Hundun Wo is the Zuqi Acupoint. The medicine of Gen Nan enters the Zuqi Acupoint from the northeast and combines with Zhenqian (True Lead, referring to Yuanjing/Kidney Qi), much like a husband and wife tying their silk ropes. However, upon initial return, they do not yet condense; one must tightly close the Six Gates, regulate breath continuously, and use Shenhuo (Spirit Fire) to fumigate, causing them to merge into one. Yet, the Huohou for combining the Dan must be Wenhuo (Civil/Gentle Fire), warm and mild, unlike the Wuhuo (Martial/Intense Fire) used during Caiqu (Collection). Therefore, one must achieve Taihe Xiangqia (Harmonious Integration) to successfully initiate the process (Zhaoshou Chengchun).

Although the *Huoji* (Records of Fire) has been handed down in six hundred chapters, it has not written the true Houhou (Timing of Fire) on Luanjian (ornate paper/books).
Nothing is clearer than the words of Chongxu: "Clear breathing allows one to complete the Immortal Dao."
Zixianzi said: "Sages transmit the medicine but not the fire; since ancient times, few have known the Huohou." Ten thousand volumes of Golden Dan are not recorded in books, yet Chongxu alone said: "Though Huohou is said to be untransmittable, one must silently operate according to circumstances to enter the profound mystery. Observing past sages by the thousands, clear breathing allows one to complete the Immortal Dao." This shows that the essence of Huohou should be sought in Zhenxi (True Breath). For breath arises from the Heart; when the Heart is still, breath is regulated; breath returns to its root with each cycle; this is the mother of Golden Dan.
However, Huohou is not uniform; ancients distinguished it as internal and external. External Huohou involves action and doing, pertaining to the foundation-building stage. Internal Huohou occurs when the Dan is already obtained, allowing nature to take its course, pertaining to non-action. It fundamentally revolves around the two characters of breathing. If one does not regulate the breathing of external Huohou, one cannot circulate this Dan; if one does not regulate the breathing of internal Huohou, one cannot warm-nourish this Dan. Thus, Liu Hanyang said: "All breathing-fire can transform the grain essence of food and assist Yuanjing; all Spirit-fire can transform Yuanjing and assist Yuanqi; all Yuanqi-fire can transform breathing and assist Yuanshen; Yuanshen-fire can further transform form and return to emptiness to assist the Dao. From beginning to end, all rely on the power of fire to ascend to the Luotian Immortal realm." One must also know that Huo (Fire) and Hou (Timing) are inseparable; Fire must correspond to Timing, and when Timing arrives, Fire also arrives. Therefore, the term Huohou consists of detailed items step by step. Without transmission from a master, it remains difficult to thoroughly understand in the heart; one must cultivate virtue and illuminate the Way to seek a master's instruction.