What kind of state the brush should be in to write on paper is ideal, which is the key to the writing skill of the brush and the most basic rule of the quality of stroke writing. The brushwork is one of the important parts of China calligraphy theory. According to legend, as early as the Eastern Han Dynasty, Cai Yong wrote "Pen Collection", which was handed down from generation to generation and was regarded as a treasure by calligraphers. Ancient literati regarded brushwork as a secret. They are very conservative and never tell anyone easily.
It is said that Dan Wei, a student and calligrapher in Cai Yong, has Cai Yong's brushwork. Another calligrapher, Zhong You, wanted to borrow it, but was refused. In order to show sincerity, Zhong You beat his chest until he vomited blood and fainted. However, he failed to see the "brushwork" clearly after all, and used it as a funerary object when Wei died. Zhong You sent troops to dig graves and got Cai Yong's "brushwork", which made great progress in calligraphy. Although the legend is not credible, it is enough to prove the importance of brushwork theory.