Lanzhenzi 懶真子 "Records of the Lazy Perfect", also called Nenzhenzi 嫩真子 or Nenzhenzi lu 嬾貞子錄, is a "brush-notes"-style book (biji 筆記) written during the Northern Song period 北宋 (960-1126) by Ma Yongqing 馬永卿 (jinshi degree 1109), courtesy name Danian 大年.
The 5-juan-long book is divided into 173 short chapters that cover a wide range of themes. A great part of the topics comes from discussions between the author and his teacher Liu Anshi 劉安世 (1048-1125). Strangely enough, the Lanzhenzi is not mentioned in the bibliographies Junzhai dushu zhi 郡齋讀書志 and Zhizhai shulu jieti 直齋書錄解題, although it is mentioned in Yuan Wen's 袁文 (early 12th cent.) book Yongyou xianping 甕牖閒評, Wang Mao's 王楙 Yeke congshu 野客叢書 (1151-1213) and Fei Gun's 費袞 (c. 1200) Liangxi manzhi 梁溪漫志. The book is headed by a chapter on the historian and politician Sima Guang 司馬光 (1019-1086) and his teachings, and therefore an additional source on this important person. The Lanzhenzi talks about a wide range of themes in traditional literature and closes up a lot of errors in these writings, even of famous scholars as Ban Gu 班固 (32-92 CE), Du Fu 杜甫 (712-770) or Han Yu 韓愈 (768-824). It is therefore a helpful, yet unsystematic commentary to many ancient writings.
The Laizhenzi is included in the series Baihai 稗海, Siku quanshu 四庫全書, Zishu baijia 子書百家, Baizi quanshu 百子全書, Yangsuxuan conglu 養素軒叢錄, Biji xiaoshuo daguan 筆記小說大觀, Congshu jicheng chubian 叢書集成初編, Ruxue jingwu 儒學警悟, Songren xiaoshuo 宋人小說 (all under the name Nenzhenzi lu), Shuofu 說郛, Wuchao xiaoshuo 五朝小說, Wuchao xiaoshuo daguan 五朝小說大觀 and Jiuxiaoshuo 舊小說.