鄭人有欲買履者，先自度其足，而置之其坐。至之市，而忘操之。已得履，乃曰：“吾忘持度。”反歸取之。及反，市罷，遂不得履。人曰：“何不試之以足? ”曰：“寧信度,無自信也。”

 A man from Zheng measured the size of his feet before going to the market for a pair of shoes. He put the measurement beside where he sat. But he forgot to bring it with him to the market. Then he found a pair of shoes and said, "I forgot to bring the note of my measurement." He returned home to fetch it and went to the market again which had been closed. So, the shoes failed him. Other men asked him, "Why didnt you try the shoes for size yourself?" He replied, "I would rather believe the measurement made than my feet."