There was a man of Zheng who wished to buy shoes. First he measured his own foot and set the measurement down on his seat. When he reached the market, he had forgotten to bring it with him. Having found the shoes, he said, 'I have forgotten to bring my measurement,' and turned back home to fetch it. By the time he returned, the market had broken up, and so he got no shoes. Someone asked, 'Why did you not just try them on with your foot?' He replied, 'I would rather trust the measurement than trust myself.'