The earliest mention of alchemy in China occurs in connection with fangshi ("masters of the methods") specialists in cosmological and esoteric arts employed by rulers from the 4th century BCE.
The 3rd-century BCE Zhanguo Ce and Han Feizi both record a story about King Qingxiang of Chu (r. 298–263 BCE) being presented a busi zhi yao 不死之藥 "immortality medicine". As the chamberlain was taking the elixir into the palace, a guard asked if it was edible and when he answered yes, the guard grabbed and ate it. The king was angered and condemned the guard to death. A friend of the guard tried to persuade the king, saying, "After all the guard did ask the chamberlain whether it could be eaten before he ate it. Hence the blame attaches to the chamberlain and not to him. Besides what the guest presented was an elixir of life, but if you now execute your servant after eating it, it will be an elixir of death (and the guest will be a liar). Now rather than killing an innocent officer in order to demonstrate a guest's false claim, it would be better to release the guard." This logic convinced the king to let the guard live.