Qingnangshu 青囊書

In Chapter 78 of the Romance, Hua Tuo tells Cao Cao, who suffers from a head-wind ailment, that the root of the illness can be removed only if he first drinks Mafeitang and then has his head split open with an axe to remove the wind-phlegm. Cao Cao says that Hua Tuo is close to Guan Yu and wants to avenge him, and has him imprisoned and interrogated under torture. To the prison guard Jailer Wu, who treated him to wine and food every day in prison, Hua Tuo says that he will soon die and regrets that he has not passed the Qingnangshu on to the world, and asks him to take a letter he will write, fetch the book from his house and carry on his medical art. Romance, Ch. 78 §14–16

Jailer Wu goes to Jincheng, receives the Qingnangshu from Hua Tuo's wife and brings it back, and Hua Tuo, after looking it over, gives the book to Jailer Wu. Ten days later, when Hua Tuo dies in prison, Jailer Wu holds his funeral, quits his post and returns home to study the book, but his wife is already burning it and he saves only a page or two. His wife says that even if he learned to be as marvelous as Hua Tuo, he would only end up dying in prison. The Romance writes that for this reason the Qingnangshu was never passed on to the world, and that only trivial methods such as castrating chickens and pigs, recorded on the pages left from the fire, have come down. Romance, Ch. 78 §17–19