The Turba Philosophorum, or Assembly of the Alchemical Philosophers, is attributed to Arisleus. It is one of the earliest Alchemical texts, believed to be from the 12th Century. The Turba Philosophorum was often quoted in later Alchemical texts. Also included in this volume: Revelation of the True Chemical Wisdom by Friederich Gualdus, which includes a Forward by Hans W. Nintzel. Contained therein, are letters between Gualdus and Baron von Reusenstein. The latter refers to Gualdus as an Adept. Dr. Sigismund Bacstrom held von Reusenstein in very high regard. We have here, also, Gualdus' recipe for longevity.