The Jesuit C.F. Milliet Dechales (1621–1678), author of one of the most famous early modern mathematical encyclopedias, Cursus seu mundus mathematicus (1674), wrote a hundred-folio-page long treatise devoted to the “progress of mathematics,” which was published in the second, enlarged edition of his encyclopedia (1690). His historical treatise covers the gamut of mixed mathematics—including astronomy, mechanics, optics, music, geography and navigation, ars tignaria (art of timber-framing), and architecture. The early modern historical narratives about the mathematical sciences, from Regiomontanus’s Oratio (1464) onwards, have been aptly characterized by their literary form and goals rather than their historical content. Rhetoric, humanistic topoi, and philosophical filiation turned the histories of mathematics into powerful tools for different purposes. My account of Dechales’ tract on the “progress of mathematics” analyzes the ways in which it dovetails with Jesuit approaches to mathematics, provides legitimation to the mathematical sciences as well as to their authors, and contributes to define the role and boundaries of the discipline, in particular vis-à-vis natural philosophy.