"Bigu", also known as Quegu and Qugu, originated from Fang Xianjia's "don't eat whole grains", that is, instead of eating whole grains, it is a common way for the ancients to fill their stomachs with drugs, food and other things or fast for a certain period of time.
Pigu, often associated with persuasion, is called convincing to Pigu. Being convinced, as the name implies, is to take qi. After being influenced by Taoist thought, it is called taking essence or taking qi. This is the practice of replacing food with qi, and the method of breaking the valley with conviction is always emphasized by Taoism. Since the Han Dynasty, there has been a legend that Taoist priests were persuaded to break the valley, and there were also many imitators in previous dynasties.