Pigu means not to eat grains after activating one's mind, which is the method used by alchemists and Taoists to cultivate immortals in the past. Also known as "broken grain", "broken grain", "broken grain", "suspended grain" and "broken grain". Taoism follows that people eat whole grains and accumulate feces in their intestines, which will produce foul smell and hinder the road to immortality. "Huang Ting Neijing" says: "The land of Cooper eats essence, evil spirits smell from the outside, and the fetish of stinking gods is zero. So, how can we get the baby back from the old place? " At the same time, there are three worms (three corpses) in the human body, which depend on this kind of grain gas to survive. With its existence, people have evil desires and cannot become immortals. Therefore, if you want to clear the dirty gas in the intestine and get rid of the three corpse worms, you must break the valley. Therefore, Taoism imitates the immortal behavior described in Zhuangzi Xiaoyao Tour, hoping to achieve the goal of immortality.