In the 13th century, the library of Royaumont Abbey was one of the best endowed with documents in the kingdom. Between 1244 and 1258, the Dominican Vincent de Beauvais used them to write in Latin, with the moral support of Louis IX, the “Speculum maius” or “Great Mirror”. This three-part encyclopaedia is a compilation of ancient and medieval knowledge. In the part devoted to nature (“Speculum naturale” or “Mirror of Nature”), Beauvais wrote numerous chapters, arranged in alphabetical order, on the use of plants and animals in medicine. Up until the 17th century, Vincent de Beauvais’ encyclopaedia would remain a work of reference.