Explanation: It describes the graceful movements when waving a brush, and the light and free strokes when writing.
Source: Du Fu's "Song of the Eight Immortals in Drinking"
Original text: Zhang Xu's Three Cups of Grass, taking off his hat and uncovering his head in front of the prince, swiping paper like clouds of smoke
The meaning is: The words written by Zhang Xu (the sage of cursive script) are like clouds and smoke in the sky, which means that the cursive sage's calligraphy is superb
The full text of Du Fu's poem "Song of the Eight Immortals in Drinking":
Zhizhang Riding a horse is like riding a boat, falling into a well and sleeping under the water. The three battles in Ruyang began to face the sky, and the mouth of the road met with Qu's chariot, salivating at the mouth, and the desire to seal it to Jiuquan was unwavering.
The left prime minister spends tens of thousands of money on daily prosperity, drinks like a long whale sucking in hundreds of rivers, holds a cup in his hand, and is called a sage. Zongzhi, a handsome and handsome young man, raised his glass and looked at the blue sky with his white eyes, which was as bright as a jade tree before the wind. Su Jin Changzhai often likes to escape to Zen when he is drunk in front of embroidering Buddha. Li Bai wrote a hundred poems about drinking wine and went to sleep in a restaurant in Chang'an City.
The emperor couldn't get on the boat, so he claimed that he was a wine-drinking immortal. Zhang Xu takes off his hat and tops his head in front of the prince, swiping paper like clouds of smoke.
Jiao Sui fought five battles with Fang Zhuoran, and his eloquent talk shocked the four feasts.