Cao Cao had over twenty sons, most of whom remained obscure, but three stood out for their brilliance and learning: Cao Pi, who later became emperor; Cao Zhi, famed for composing a poem in seven steps; and Cao Chong, courtesy name Cangshu, who from childhood displayed extraordinary intelligence and was so favored by Cao Cao that he considered making him his heir.
One year, a rare and stunning pheasant was presented to Cao Cao from the south. The envoy explained that the bird loved to dance by clear rivers and sing beautifully. Intrigued, Cao Cao wanted to see it perform, but the pheasant refused to move, ignoring all the ministers' coaxing.
The ministers were at a complete loss, all agreeing that only Cao Chong could solve the problem. Cao Cao nodded in approval and summoned Cao Chong.
Why would the court officials seek advice from a mere five or six-year-old child? The answer lay in Cao Chong's extraordinary intelligence, as he had recently solved a problem that had stumped even the most learned scholars.
When Sun Quan gifted Cao Cao a massive elephant, northerners who had never seen such a creature marveled at its size. Cao Cao, curious about its weight, ordered his ministers to find a way to weigh it. With no scale large enough, they racked their brains in vain. Then Cao Chong, a young son of Cao Cao, interjected, "What's so hard about that? Simply place the elephant on an empty boat, mark how deep the boat sinks, then lead the elephant ashore. Load the boat with stones until it sinks to the same mark, then weigh each stone separately—won't that give you the elephant's weight?"
Following Cao Chong's instructions, Cao Cao's men successfully weighed the elephant. The court officials praised the boy's cleverness, and Cao Cao himself was beaming with joy.
Now everyone faced another difficult problem, and naturally, they thought of Cao Chong again.
When Cao Chong arrived, the problem was solved at once. He ordered his attendants to bring a large bronze mirror and set it upright before the pheasant.
A gleaming bronze mirror reflected the pheasant's own beautiful form. Seeing its own splendid feathers in the mirror, the pheasant became overjoyed, crowed loudly, spread its wings, and began to dance gracefully.
When Cao Cao saw the mountain pheasant finally begin to dance, he was overjoyed and repeatedly exclaimed, "Wonderful!" The ministers, too, were full of praise for Cao Chong's extraordinary wisdom.
The pheasant leaped tirelessly, again and again, until utterly exhausted, it collapsed and died.
Tragically, this prodigiously gifted boy, Cao Chong, died at just thirteen years old. His father, the warlord Cao Cao, was devastated by the loss of his ideal successor for his grand ambitions.
Later, people used the idiom "Mountain Chicken Dances Before a Mirror" to describe self-pity.
Source: Liu Jingshu (Liu Song Dynasty), *Garden of Marvels*
Meaning of the Idiom: Later, the Chinese idiom "山鸡舞镜" came to describe how self-pity.