Jabir ibn Hayyan

The Jabirian corpus, dated to roughly 850-950, covered everything from cosmology and medicine to logic and grammar, but its core was alchemy and the theory it called "the science of the balance" - an attempt to reduce all matter to measurable proportions. The works contain the oldest systematic classification of chemical substances and the sulfur-mercury theory of metals that dominated mineralogy into the eighteenth century. They also carried early Shi'ite theological doctrines, attributed to the Imam Jaʿfar al-Ṣādiq. By the tenth century, Islamic scholars already doubted whether a single historical Jabir existed. Modern consensus holds that the name was a pseudonym for an anonymous school of alchemists. In the thirteenth century, a European writer adopted the Latinized form - Geber - and began producing new works under the borrowed mask.