In alchemy, an athanor is a furnace used to provide heat for alchemical digestion. An athanor is a self-feeding furnace, designed to maintain a uniform temperature.The athanor was also called Piger Henricus, Slow Harry, because it was chiefly used in slower operations, and because when once filled with coals, it keeps burning a long time. For this reason the Greeks referred to it as "giving no trouble", as it did not need to be continually attended. It was also called the Philosophical furnace, Furnace of Arcana, or popularly, the Tower furnace.
In the work Life of Apollonius by Philostratus the Athenian, an allegorical description is given of an occult hill. The author gives this hill the name "Athanor".