Le'an yishu 樂庵遺書 "Remnant writings of the Studio of Joy" is a book written during the early Southern Song period 南宋 (1127-1279) by Li Heng 李衡 (1100-1178), courtesy name Yanping 彥平, style Le'an 樂庵 (also written 樂菴), from Yangzhou 揚州, Jiangsu. He began his career as district magistrate of Liyang 溧陽 and was then investigating censor (jiancha yushi 監察御史), Director of the Bureau of Honours (sifeng langzhong 司封郎中), supervising scribe in the Bureau of Military Affairs (shumiyuan jianxiang 樞密院檢詳), prefect of Wuzhou 婺州, and finally secretarial censor (shi yushi 侍御史).
His book has a length of 4 juan and was actually compiled after Li's passing away by one of his friends, Gong Yu 龔昱, with the title Le'an yulu 樂庵語錄 "Sayings of Le'an Studio". This title was later changed to "remnant writings". The book speaks a lot of Neo-Confucian issues like the human mind and human nature (xin xing 心性), but with a kind of vocabulary that was prevalent during the high and late Ming period 明 (1368-1644). Moreover, the wording of the preface, allegedly written by Wu Renjie 吳仁傑 (jinshi degree 1178), is also not coherent with Wu's typical style of writing. The books thus seems to be a forgery of the Ming period, intentionally attributed to Song-period writers. The book has nonetheless some value for understanding Neo-Confucian thought.
The book is included in the series Siku quanshu 四庫全書.