What is any one of the four substances, sulphur, sal ammoniac, quicksilver, or arsenic (or, according to some, orpiment). The four spirits and the bodies seven. Chaucer called?

spirit — (Alchemy) Any one of the four substances, sulphur, sal ammoniac, quicksilver, or arsenic (or, according to some, orpiment). The four spirits and the bodies seven. Chaucer. (Webster's 1913.)