［2］In the late Han Dynasty ofancient China, a warlord called Cao Cao had a son named Cao Chong. Hewas famous as a child prodigy, and was believed to have theintelligence of an adult when he was just five years old. He is alsothought to have figured out the answer to a difficult problem, thatof weighing an elephant. Cao Chong used the principle of buoyancy tofind the solution.

According to theRecords of Three Kingdoms by Chen Shou, the southern warlordSun Quan sent a gift of an elephant to Cao Cao, who wished to knowthe animal's weight. No one could think of a method of finding it outuntil young Cao Chong had a clever idea. His solution was similar tothat of Archimedes when he faced the problem of figuring out thevolume of King Hiero's crown. Cao Chong had the elephant loaded ontoa boat, on which the water level was marked. The elephant was thenreplaced with smaller weighable objects until the boat was submergedto the same level. It was then possible to calculate the weight ofthe elephant by adding up the weights of all the objects.

On another day, Cao Caowanted to ride his horse, but his saddle had been chewed through byrats. The warehouse keepers who looked after the saddles were ingreat fear for their lives since the law was very strict. Cao Chongsaved them by taking a knife and cutting holes in his own clothes tomake them look as if they had been chewed by rats. He showed them tohis father, who thought that the rats were so widespread that thewarehouse keepers could not be blamed for what had happened to the saddle.