Lantingkao 蘭亭考 "Analysis of the essay of the Orchid Pavilion" is a critical study to Wang Xizhi's 王羲之 (303-361) famous calligraphy Lantingxu 蘭亭序 from the Jin period 晉 (265-420). The 12-juan long book was compiled during the Song period 宋 (960-1279) by Sang Shichang 桑世昌, courtesy name Zeqing 澤卿.
The original title of the book was Lanting boyi 蘭亭博議 and had a length of 15 juan, but the title was later changed by Gao Sisun 高似孫 (1158-1231), who also abbreviated Sang's study.
The calligraphy of the short essay Lantingxu that was compiled in 353 CE had for centuries served as a model calligraphy of the running script (xingshu 行書). The calligraphy is 324 characters long and written in 28 columns, and the text describes the opportunity in which a meeting of poets and scholars met at a banquet. The Lantingkao investigates the history of the the calligraphy, its preservation by Wang Xizhi's descendant Wang Zhiyong 王智永 and later by Emperor Taizong 唐太宗 (r. 626-649) of the Tang dynasty 唐 (618-907), who ordered Zhao Mo 趙模 to produce copies of the calligraphy that were to serve as models for practicing calligraphy. The original has vanished, but Zhao Mo's copies helped preserving the style of Wang Xizhi.
According to another tale, the calligraphy had been cut into a mountain cliff, where the early Song scholar Li Xuejiu 李學究 detected it and preserved the copy. His son sold this copy to the famous historian Song Qi 宋祁 (998-1061), Marshal Dingwu 定武帥. Song Qi cut it into stone as the so-called Dingwu version 定武本. Sang Shichang also tried to find out the age of Wang Xizhi in the year 9 of the Yonghe reign (Yonghe jiu nian 永和九年, the first words of the calligraphy), when the text was compiled. Wang must have been 51 years old and not, as other scholars say, 33.
The Lantingkao had disappeared for some time after Sang Shichang entered a monastery, but was later rediscovered. It is included in the series Siku quanshu 四庫全書, Zhibuzuzhai congshu 知不足齋叢書 and Congshu jicheng chubian 叢書集成初編.