Didascalicon, Book II: the sciences, their parts and their discipline
Chapter XIV. On geometry
Geometry has three species: planimetry, altimetry, cosmimetry. Planimetry measures the plane, that is the long and the broad, and extends forward and back, right and left. Altimetry measures the high, and extends upward and downward. For the sea too is called high, that is deep; and a tree high, that is lofty. Kosmos is interpreted the world, and hence cosmimetry is so called, that is, measure of the world; this measures the spherical, that is the globular and round, as a ball and an egg, whence also from the sphere of the world, on account of its excellence, it is called cosmimetry, not because it treats only of the measure of the world, but because the sphere of the world is the most worthy of all spherical things.