《左传·僖公·僖公二十三年》
重耳到达曹国，曹共公听说他的肋骨排比很密，似乎并成一整块，想从他裸体中看个真相。
及曹，曹共公闻其骈胁，欲观其裸。
Chong'er arrived in the State of Cao, and Duke Gong of Cao heard that his ribs were very closely spaced, as if they were one piece, so he wanted to see the truth by stripping him naked.