On a bridge at Xiapi, the young Zhang Liang met an old man in coarse clothes who dropped his shoe under the bridge. “Boy, go down and get my shoe!” Zhang Liang was startled and wanted to hit him, but because the man was old, he held back and fetched it. “Put it on me!” the old man said. Zhang Liang knelt and did so. “The boy can be taught,” said the old man.
He told Zhang Liang to meet him at dawn five days later. Twice Zhang Liang came after the old man and was sent away. The third time, he came before midnight. The old man gave him a book, the Art of War of the Grand Duke. Zhang Liang later used it to advise Liu Bang, who followed his plans. (Records of the Grand Historian)