Story of the fool that was his own doctor.
For instance, there was a man suffering from flatulence. And once on a time the doctor gave him a medicine, to be used as a clyster, and said to him, “Go to your house, and bruise this, and wait till I come.” The physician, after giving this order, delayed a little, and in the meanwhile the fool, having reduced the drug to powder, mixed it with water and drank it. That made him very ill, and when the doctor came, he had to give him an emetic, and with difficulty brought him round, when he was at the point of death. And he scolded his patient, saying to him, “A clyster is not meant to be drunk, but must be administered in the proper way. Why did you not wait for me?”
“So an action, useful in itself, if done contrary to rule, has bad effects. Therefore a wise man should do nothing contrary to rule. And the man, who acts without consideration, does what is wrong, and immediately incurs reproach.”