There are two books with the title Caoshu shi 草書勢 "The forces of the grass script".
Caoshu shi 草書勢 is an essay on calligraphy written during the Later Han period 後漢 (25-220 CE) by Cui Yuan 崔瑗 (77-142 CE), courtesy name Ziyu 子玉, who was administrator (xiang 相) of the Prince of Jibei 濟北. Cui was a disciple of the famous calligrapher Du Du 杜度 (mid-1st cent. CE). The essay is the oldest Chinese text on the cursive writing style called "grass script" (caoshu 草書). Cui advocates the use of the cursive grass script to make communication easier in the vast field of administration because the writings style was easier to use and the seal script (zhuanshu 篆書) or the chancery script (lishu 隸書). The grass script was more flexible and was not subject to the strict rules of the "old-style" scripts (gushi 古式), but instead attenuated the rigid principle of that "squared must be centered by a ruler, and circles must be accompanied by a pair of compasses" (fang bi zhong gui, yuan xu fu gui 方必中矩、圓須副規). Yet this did not mean that the grass script led to chaotic captions, because the caoshu-type script, too, had to pay attention to the subtlety of slender brush strokes, and to respect the right appropriate position in the context (xianwei yao miao, linshi cong yi 纖微要妙,臨事從宜).
Seen from the artistic aspect, Cui Yuan compares the appearance of grass-script texts with animals:
獸跂鳥跱,志在飛移;狡兔暴駭,將奔未馳。[...] 旁點邪附,似螳螂而抱枝。[...] 若山蜂施毒,看隙緣巇;騰蛇赴穴,頭沒尾垂。 | Birds and beasts raising their heels, ready to fly and run away; terrified rabbits, right about to flee... Dots and strokes by the side, looking like an mantis holding a twig... Like a mountain wasp applying its poison, looking for a crevice in the gorge, [like] the (legendary) flying snake hurrying towards its cave, head and tail bent down. |
These appearances were the result of emotions and moods lasting during the writing process, a phenomenon not occurring by the use of seal or chancery script.
Caoshu shi 草書勢, Caoshu zhuang 草書狀 or Shushi 書勢 is an essay on calligraphy written during the Western Jin period 西晉 (265-316) by Suo Jing 索靖 (239-303), courtesy name You'an 幼安, posthumous title Zhuang Jing 莊靖, from Dunhuang 敦煌 (today in Gansu). He was governor (taishou 太守) of the commanderies of Yanmen 雁門 and Jiuquan 酒泉, and was later appointed General of the Left Guard (zuowei jiangjun 左衛將軍) Because he held the title of Cavalry Commander Conquering the West (zhengxi sima 征西司馬), he was also referred to as Suo Zhengxi 索征西. Suo was famous for his calligraphic style, and for his "separated-character grass script" (zhangcao 章草) in particular. He was even proud of his own artworks (of which copies of the Qiyue tie 七月帖, Yueyi tie 月儀帖, Chushi song 出師頌, Jijiuzhang pian 急就章篇, and Wuqiu Xing bei 毋丘興碑 have survived). His book Suozi 索子 is lost.
Suo Jing's essay narrates the origin of the zhangcao writing style, from the quickly written "clerical grass script" (licao 隸草). The author calls the appearance of the grass script "silver hooks with scorpion tails" (yin gou chai wei 銀鈎蠆尾), which is only one of many zoological and botanical metaphors he used to express the vivid style of the script.
蓋草書之爲狀也,婉若銀鈎,漂若驚鸞,舒翼未發,若舉復安。 | The shape of the grass script is elegant as silver hooks, floating in grace as frightened phoenixes whose wings are not yet unfolded when calming down again. |
舉而察之,又似乎和風吹林,偃草扇樹,枝條順氣,轉相比附,窈嬈廉苫,隨體散布。 | When we look at [the written words], it seems that the wind is blowing in the woods, laying down the grass and shaking the trees, bending the branches so that they obey the airs. One detail goes over into the next, and the soft and slender parts are scattered over the whole [text]. |
或若登高望其類,或若既往而中顧,或若倜儻而不群,或若自檢于常度。 | Some [characters] appear as if looking down at their fellows, some seem to go forward while looking back, some of them are setting themselves apart from the others, while yet others seem to check themselves. |
Because the text was written hastily in order to reflect the "energetic" (shi 勢) style of the script, some commentators had the impression that the text was a fragment.
The text is quoted in Suo's bibliography in the official dynastic history Jinshu 晉書, in Zhu Changwen's 朱長文 book Mochibian 墨池編 (1039-1098), Chen Si's 陳思 (1225-1264) Shuyuan jinghua 書苑菁華 (where it is called Suo Jing xu caoshu shi 索靖叙草書勢), and in the series Yuhanshanfang jiyi shu 玉函山房輯佚書 and Lidai shufa lunwen xuan 歷代書法論文選.