In the State of Zheng, the word "Pu" referred to uncarved jade. However, in the State of Zhou, the same word meant an unsalted mouse.
Once, a man from Zhou, carrying a dead mouse in his pocket, approached a merchant from Zheng and asked if he wished to buy a "Pu". The Zheng merchant, assuming it was a piece of uncarved jade, readily agreed.
When the man from Zhou produced the dead mouse, the merchant firmly refused to buy it.