In the State of Zheng, a man decided to go to town to buy a new pair of shoes.
Before leaving home, he measured his foot with a piece of straw to use as a measurement. Upon arriving at a shoe shop, he reached into his pocket only to realize that in his haste, he had left the measurement at home. He immediately turned around and hurried home to fetch it.
When he rushed back to the shop with the straw, it had already closed. His entire trip had been in vain.
Later, someone asked him, "Were you buying shoes for yourself or for someone else?"
"For myself," he replied.
Another person asked, "Don't you have your own feet with you? You could have simply tried the shoes on to find the right size. Why did you go all the way home for the measurement?"
The man from Zheng insisted, "I would rather trust the measurement than my own feet."