Philosopher's stone
The Rosarium Philosophorum is itself an alchemical collection, taking the form of a (florilegium), or a collection of citations of earlier alchemical authorities, among them Khalid ibn Yazid, Pseudo-Arnaldus of Villa Nova, Alphidius, and Pseudo-Lull) and which includes verses explaining the preparation of the Philosopher's stone accompanied by allegorical illustrations, which depict, for example, the union of the male and female principles. The collection is preserved in many manuscript copies and comes perhaps from the end of the fourteenth or the beginning of the fifteenth century (some even date it to the sixteenth century).