The Tanyuan tihu 譚苑醍醐 "Refined butter from the garden of discussions" (also written 譚菀醍醐)
is a biji 筆記 "brush notes" style book written by the Ming period 明 (1368-1644) scholar Yang Shen 楊慎. The 9 juan "scrolls" long book was finished in 1542. In the preface the author explains that the title has been chosen according to a proverb which says that animals produce milk, milk becomes butter, and butter is turned into clarified butter (tihu 醍醐), which is a symbol of wisdom or purity. Yang Shen wanted to express that his book was something written in his old, "refined" years. It includes a lot of interesting information about ancient texts and adds valuable comments to these. He found out, for instance, that Nangong Shi 南宮適, who is mentioned in the Confucian Classic Shangshu 尚書 "Book of Documents", was the same person as Nangong Baida 南宮百達 (or Nangong Boda 南宮伯達), or that the chart of the Former Heaven (xiantiantu 先天圖) was invented by Xi Yi 希夷, and that of the Later Heaven (houtiantu 後天圖) by Kang Jie 康節, some generations earlier, but in the same line of teachers, which had not been found out by the great Neo-Confucian master Zhu Xi 朱熹 (1130-1200). Another example is the story of how the military strategist Zhuge Liang 諸葛亮 built a makeshift bridge of bamboo in order to attack Sima Yi 司馬懿 which is not reported in the official history Sanguozhi 三國志, but quoted in the Shuijingzhu 水經注. In some instances Yang Shen is able to rectify textual errors, like the sentence youjun qinzhen 右軍清真 in the Shishuo xinyu 世說新語 which was erroneously transformed into youjun qinggui 右軍清貴 in some editions. In this case, a quotation in a poem by Li Bai 李白 served to unveil the mistake.
The Tanyuan tihu is to be found in the reprint series Siku quanshu 四庫全書 and Hanhai 函海 (in a 8-juan version) that has been reproduced in the Congshu jicheng chubian 叢書集成初編.
Source: Li Xueqin 李學勤, Lü Wenyu 呂文鬰 (1996). Siku da cidian 四庫大辭典, Changchun: Jilin daxue chubanshe, vol. 2, p. 1926.