The Bencao gangmu, known in English as the Compendium of Materia Medica or Great Pharmacopoeia, is an encyclopedic gathering of medicine, natural history, and Chinese herbology compiled and edited by Li Shizhen and published in the late 16th century, during the Ming dynasty. Its first draft was completed in 1578 and printed in Nanjing in 1596. The Compendium lists the materia medica of traditional Chinese medicine known at the time, including plants, animals, and minerals that were believed to have medicinal properties. Li compiled his entries not only from hundreds of earlier works in the bencao medical tradition, but from literary and historical texts. He reasoned that a poem might have better value than a medical work and that a tale of the strange could illustrate a drug's effects. The Ming dynasty emperors did not pay too much attention to his work, and it was ignored. Li's work contained errors and mistakes due to his limited scientific knowledge at the time. For example, Li claimed that all otters were male and that quicksilver (mercury) was not toxic. The title, translated as "Materia Medica, Arranged according to Drug Descriptions and Technical Aspects", uses two Chinese compound words. Bencao (Ban-chao; "roots and herbs; based on herbs, pharmacopeia, materia medica") combines ben ( 'origin, basis') and cao ( 'grass, plant, herb'). Gangmu (Kang-mu; 'detailed outline; table of contents') combines gang (kang; 'main rope, hawser; main threads, essential principles') and mu ( 'eye, look; category, division'). The characters and were later used as 'class' and 'order', respectively, in biological classification. Li Shizhen travelled widely for field study, combed through more than 800 works of literature, and compiled material from the copious historical bencao literature. He modelled his work on a Song dynasty compilation, especially its use of non-medical texts. He worked for more than three decades, with the help of his son, Li Jianyuan, who drew the illustrations.