Sun Quan once sent Cao Cao a large elephant. Cao Cao wanted to know its weight, but none of his officials could work out how. His young son Cao Chong said: “Put the elephant on a big boat and mark where the water reaches. Then load the boat with things that can be weighed, and the answer will be known.” Cao Cao was delighted and did it. (Records of the Three Kingdoms)
The story may not be true. The scholar He Zhuo argued that Sun Quan could only have obtained elephants after 210, and Cao Chong died before then, in 208 at the latest. The historian Chen Yinke argued that the story came from an Indian Buddhist text.