According to legend, Cai Yong was ecstatic when he got the ancient books in Songshan. After drinking tea for three days, he didn't want to eat it, and then he studied for three years. He is so fascinated that he uses his pen skillfully. He is also good at observing life, from which he realizes brushwork, and his calligraphy has made great progress.
During the reign of Emperor Ling of Han Dynasty, Cai Yong went to Hongdumen to wait for the emperor to summon him. At that time, craftsmen were renovating Hongdu Gate and brushing white powder on the wall with brooms. Observing carefully, he saw that his hair turned white after brushing, and inspiration flew to him. After his return, he created a new style of writing-"flying white book". This kind of books are natural and simple, vigorous and powerful, full of momentum, such as flowing water, electricity turning like a pen, full of interest, and have great influence at that time and later generations. Zhang Huaiguan said in Book Break: "Cai Yong's flying white is so gorgeous, and the escape of words is no longer here."