Liu Zongyuan fell ill and summoned a renowned doctor for diagnosis. The doctor examined him and said, "Your spleen is swollen. You will recover by taking high-quality poris cocos (fuling)."
Liu Zongyuan sent a servant to purchase the herb from an apothecary. He brewed and drank the decoction, but instead of improving, his condition worsened.
Suspecting the doctor had prescribed the wrong medicine, Liu summoned and reproached him, demanding an explanation.
The doctor, unconvinced of his error, poured out the dregs from the pot for examination. To his astonishment, they were not poris cocos, but merely dried sweet potatoes that had been dyed and processed.
The doctor sighed and remarked, "The medicine seller is a swindler, and the patient cannot distinguish genuine from fake. An illness cannot be cured by the doctor alone."