Liu Zongyuan was ill. He called a famous doctor for diagnosis and treatment. The doctor said: "Your spleen is swollen. You will get well by taking good quality fining (poris cocos)."
Liu Zongyuan sent someone to buy fining from a herbal medicine shop, boiled it and drank the decoction. However, his illness was not relieved, but turned worse instead.
Thinking that the doctor had prescribed the wrong medicine, he called and reproved him, asking what was the matter.
The doctor didn't believe this. He poured out the dregs of the decoction from the pot and examined them. To his surprise, they were not fining, but just dried sweet potatoes, dyed and processed.
The doctor sighed and said: "The medicine seller is a swindler. The medicine taker does not know head or tail of it. Illness cannot be cured by the doctor alone."