Source: Journey to the West.
Then there is the distinction between hidden and not hidden. Immortal ancient books have always used argot, what lead and mercury, what dragon and tiger, what tortoise and jade rabbit, and so on. Actually, it's all code words. Most people don't have a biography of the master, so they can't make a strong guess. If they practice with strong guesses, they will be possessed by magic pills. People who cultivate truth always look for immortals to visit Taoist temples and find a true teacher in order to get a guide. The formula says that revealing secrets can also be euphemistic. In fact, it is just the connotation of double cultivation in life. There is no other way to say that life is one, that is, wit reveals the secret.
Although the recipe of expanded materials was secretly passed to Wukong's top-grade fairy recipe by Bodhi's ancestor (later said by Wukong during the war with the black bear essence), it was actually pieced together by the original author with reference to the classics and Buddhist techniques of the fairy family. Wu Cheng'en's three religions are bypassed, and poetry is easy to write. This formula is of little practical use, otherwise Wu Cheng'en would have been thoroughly remoulded and become an immortal! The woodcutter has nothing to do, so he will explain it in detail, hoping that everyone will have a preliminary understanding of Taoist culture. As for Neidan's practice;
The founder of Zhang Sanfeng once said: "Even if you are the number one scholar in seven subjects, without the guidance of a famous teacher, it is purely blind practice!" Bad temperature will hurt your body and mind, and even be possessed! Therefore, the above is only a preliminary understanding of reference, that is, it is not of great practical use, and the actual training still needs a noble teacher to guide. Normally speaking, the cultivation of Neidan requires a hundred days to build a foundation, three years to keep warm and ten years to face the wall. Full of hardships and carelessness, it is more difficult to be possessed than to be the richest man in the world. It is said that the immortal house only conveys strength and purity.