Mengxi bi tan (Jottings at the Dream Brook Studio) was written in encyclopedic form as a collection of hundreds of articles by Shen Kuo (1031−95), a Song polymath, scientist, statesman, and artist. The work was written at Mengxi (Dream Brook) Garden, his estate in Runzhou (near present-day Zhenjiang, Jiangsu), thus the title. This work’s extraordinarily broad coverage includes astronomy, physics, mathematics, geology, geography, biological medicine, contemporary politics, military affairs, economics, and anecdotes about the arts and literature. It is also a very important document in the history of Chinese science, summarizing many discoveries during the Northern Song dynasty (960−1127), and thus providing a valuable source on the political, scientific and technological, and economic developments of the time. Among the subjects covered are the first known movable-type printing press (the invention of Bi Sheng, 990−1051). The earliest printed edition of this work was issued in the ninth year (1305) of the Dade reign of the Yuan dynasty. It was printed by Chen Renzi, style name Guyu, at his Dongshan Shuyuan (Academy at the East Mountain), the largest private printing workshop of the time in south China. The reprint was based on an edition from the Qiandao reign (1165−1173) of the Southern Song dynasty and is thus in Song style. The work is in butterfly-fold binding. The pages are spacious, but the text area is very small, in a distinctive style. It is a fine representative of Yuan printing. This is the only copy in existence. It was kept in the imperial collection during the Yuan and Ming and later entered into the collections of famed bibliophiles, such as Wang Shizhong. In 1965 Premier Zhou Enlai facilitated its purchase for a large sum from Chen Qinghua, a collector living then in Hong Kong, and it is now in the collections of the National Library of China. Shown here are the prefaces, table of contents, and four juan of Mengxi bi tan.