《礼记·礼运》
孔子曰： 我曾想研究一下夏代的礼，所以特地跑到祀国考察，但因年代久远，留下的文献太少，只得到了一种叫《夏时》的书。
孔子曰： 我欲观夏道，是故之杞，而不足征也；吾得夏时焉。
Confucius said: "I once wanted to study the etiquette of the Xia Dynasty, so I went to the nation to investigate. However, because of the long history, there were too few documents left, and I only got a book called "Xia Shi".