The “Scientific Revolution” of the seventeenth century cannot adequately be assessed without an appreciation of the achievements and limitations of those, whether giants or dwarfs, on whose shoulders Galileo and his contemporaries stood. And since for many historians Galileo's main contribution lies in the mathematization of the natural world and especially of time and motion, particular interest attaches to medieval treatises dealing with these questions, above all to those which were in widespread demand early in the sixteenth century.