In the reign of Emperor the Second of the Qin Dynasty (qín cháo 秦朝,221-207 BC), the prime minister Zhao Gao (zhào gāo 赵高), obsessed with ambitions, was planning to usurp the throne day and night. But he did not know how many of the ministers in the court were allowed to be ordered about by him and how many of them were his opponents. So he thought out a way to test how high his prestige among the ministers was and also to find out who dared to oppose him.

In the Warring States Period (zhàn guó 战国), the State of Zhao (zhào guó 赵国) had a famous general called Zhao She, whose son, Zhao Kuo, was very fond of reading books on military science and discussing strategy. He could recite military texts by heart, and when discussing warfare he spoke so clearly and logically that it seemed that even his father was not his match. When the State of Qin attacked the State of Zhao, the ruler of Zhao ordered Zhao Kuo to lead 400,000 men to resist the attack. But since Zhao Kuo had no practical experience of battle, he was defeated and lost his life.
Later people used this idiom to describe those who are good only at theorizing, and lack practical experience.

This legend is about Li Bai (lǐ baí 李白), a great poet in Tang Dynasty (táng cháo 唐代). Li Bai was naughty and disliked study when he was a child. One day he saw an old woman grinding an iron rod on a big stone when he was playing by a river.

 

Yi Qiu was known as the most famous expert at chess throughout the land. Once he gave lessons on chess to two men. One of them was completely absorbed in his teaching, listening attentively to Yi Qiu while the other, who seemed to be listening, had his mind on something else.

A man of the state of Chu (chǔ guó 楚国) had a spear and a shield for sale. He was loud in praises of his shield.
"My shield is so strong that nothing can pierce it through."
He also sang praises of his spear.
"My spear is so strong that it can pierce through anything."
"What would happen," he was asked, "if your spear is used to pierce your shield?"
It is impossible for an impenetrable shield to coexist with a spear that finds nothing impenetrable.