A great calligrapher in the Tang Dynasty, famous for his cursive script, who is known as the "sage of grass"?

Cao Sheng, Zhang Xu, a calligrapher in the Tang Dynasty, is as famous as Li Bai and He. Tang Wenzong once wrote a letter, regarding Li Bai's poems, Pei Min's sword dance and Zhang Xu's cursive script as "three unique skills". He also wrote poems, and was called "Four Gentlemen of Wuzhong" with He, Zhang and Bao Rong. There are "Stomach Pain Sticks" and "Four-character Poems" handed down from ancient times. 1. In the history of calligraphy in China, there are two grass saints, one is Zhang Zhi in the later Han Dynasty and the other is Zhang Xu in the Tang Dynasty. In the 20th century, two new grass saints appeared in China, one was Yu Youren and the other was Lin Sanzhi. "Cao Sheng" generally refers to Zhang Xu.