Bencao gangmu
In his government position, Li was able to read rare medical books. He began correcting some of the mistakes and conflicting information in these medical publications. He soon began the book "Compendium of Materia Medica" to compile correct information with a logical system of organization. A small part was based on another book which had been written several hundred years earlier, "Jingshi Zhenglei Beiji Bencao" ("Ching-hsih Cheng-lei Pei-chi Pen-tsao"; "Classified Materia Medica for Emergencies") – which, unlike many other books, had formulas and recipes for most of the entries. In the writing of the "Compendium of Materia Medica", he travelled, gaining first-hand experience with many herbs and local remedies and consulted over 800 books.