"His Secret Book" is attributed to Artephius, circa 1126, who was an Alchemist from Al-Andalus (the name given to Islamic Spain). Artephius was one of the most prominent Alchemists in the Middle Ages and the author of numerous works on Alchemy. "His Secret Book" describes the entire process of preparing the Philosopher's Stone. Three separate operations are described: 1.Preparation of the Secret Fire, which is the solvent used in the Work; 2.Preparation of the mercury from antimony and iron; and 3.Preparation of the Stone itself. The operations are not presented in order, and as in many works on Alchemy, the language is obscure: several names can refer to the same thing, and sometimes one name can refer to several things. Overall, however, it is a very clearly written text well worth further study.