 Johann Kepler (1571–1630) made abundant use of infinitesimals in his calculations. In his Nova Stereometria of 1615, a work actually written as an aid in calculating the volumes of wine casks, he regards curves as being infinilateral polygons, and solid bodies as being made up of infinitesimal cones or infinitesimally thin discs (Baron 1969 [1987: 108–116]; Boyer 1939 [1959: 106–110]). Such uses are in keeping with Kepler’s customary use of infinitesimals of the same dimension as the figures they constitute; but he also used indivisibles on occasion. He spoke, for example, of a cone as being composed of circles, and in his Astronomia Nova of 1609, the work in which he states his famous laws of planetary motion, he takes the area of an ellipse to be the “sum of the radii” drawn from the focus.