The *Xishan Ji* (Record of Mount West) states: Entering the Dao through techniques makes the Dao not difficult; seeking immortality through the Dao makes immortality very easy. Seeking immortality is not difficult; the difficulty lies in the fact that the Dao studied is incorrect. Studying the Dao is not difficult; the difficulty lies in the fact that the techniques practiced are not authentic. In ancient times, people could become invisible and change their appearance, retain their qi and restore their soul, use spells to prevent white blades from causing injury, use incantations to prevent poisonous insects from harming them, make nails fall off by themselves, walk on fire without burning, make water flow backward, reverse wind and rain, throw a towel to the ground to make a rabbit appear, insert a needle into a coiled belt to make a snake move—all these effects were achieved in an instant. Dragons and fish swam within moments. Such things belong to "shu" (techniques/skills), which differ from "fa" (methods). Therefore, the ancients believed that after winter, when yang qi begins to generate, residual cold qi entering the stomach and intestines after the Spring Equinox causes diseases like Shanghan (Cold Damage). Upon realizing this, one should immediately reside in a quiet room, sit cross-legged upright, close the eyes, calm the mind, and regulate breathing to stabilize the qi. Interlace both hands to cup the external kidneys (testicles), bow forward in kneeling prostration no more than twenty or thirty times. When cool sweat appears, the cold qi dissipates naturally. For cases of nocturnal emission or deficiency-cold in the lower yuan, the ancients would sit quietly in a dark room after sunset, cup the external kidneys with one hand, and rub below the navel eighty-one times. Rubbing the hands while cupping the kidneys, and cupping the hands while rubbing the navel, each for eighty-one repetitions, completed nine cycles, merely switching left and right hands. This replenishes and warms the Danyuan (Elixir Field), filling the body with true qi. By dwelling in a quiet room, cutting off distracting thoughts and forgetting speech, directing heart-fire downward, and visualizing with closed eyes as if a wheel of fire burns brightly, the Qihai (Sea of Qi) becomes firm over days, and the complexion improves remarkably. After a long time, impurities are expelled from the lower body, making one naturally resistant to cold and heat. For excessive eating leading to chest fullness, or stagnation of cold-heat, or pain and obstruction, one should sit quietly, inhale clear qi through the nose, keep the mouth tightly closed, inhale much and exhale little, attacking the diseased area. Only release the breath when it is extremely tight, repeating three to five times. The condition will naturally resolve, permanently eliminating myriad diseases. The ancients held that the upper part of the body belongs to yang, where yin cannot reach; the lower part (kidneys) belongs to yin, where yang cannot arrive. Thus, above the Yongquan (Spring Under Foot) acupoint, qi rises but does not descend, and blood flows down but does not rise, causing heaviness in the feet and knees, with yin condensing and yang scattering. Moreover, with all-day rushing and no rest, soaking the feet in hot water at night helps. However, this yields little benefit compared to elevating the legs, allowing qi to flow backward to Yongquan and逆流 (counter-flow) to the Danque (Elixir Palace), resulting in light feet on the same day, walking as fast as a galloping horse. For minor ailments of the four limbs, slight disorders of the five zang organs, or stagnation and blockage, one should sit quietly to clarify the mind, close the eyes to cut off thoughts, direct mental qi to the diseased area, hold the breath briefly, and there is no ailment that cannot be overcome. All the above are "fa" (methods), distinct from "Dao". The Dao encompasses everything and penetrates all; it is far more than mere technical skill or the ability to treat disease. Through shu (techniques), one understands fa (methods); through fa, one understands Dao. The Dao is fundamentally one yin and one yang. Yin and yang interact and combine, giving rise to the four seasons of spring, summer, autumn, and winter in heaven and earth, and the four phases of waxing, full, waning, and new moon in the sun and moon. As for humans, within a single day: at the end of Chou hour and beginning of Yin hour, yang combines with yin; at the end of Chen hour and beginning of Si hour, yang interacts with yang; at the end of Wei hour and beginning of Shen hour, yin combines with yang; at the end of Xu hour and beginning of Hai hour, yin interacts with yin. To comprehend the interaction and combination of yin and yang—how far is the Dao?