 While in Breda, Descartes met Isaac Beeckman, a Dutch mathematician and natural philosopher. Beeckman set various problems for Descartes, including questions about falling bodies, hydrostatics, and mathematical problems. Descartes and Beeckman engaged in what they called “physico-mathematica,” or mathematical physics (10:52).  Since antiquity, mathematics had been applied to various physical subject matters, in optics, astronomy, mechanics (focusing on the lever), and hydrostatics. Beeckman and Descartes brought to this work a commitment to atoms as the basic constituents of matter; as had ancient atomists, they attributed not only size, shape, and motion but also weight to those atoms (10:68). Descartes opened a section in his notebook entitled “Democritica” (10:8), in honor of the ancient atomist Democritus.