 Based on the autobiographical narrative included in Part One of the Discourse on Method (1637), where Descartes describes what he learned when he was “at one of the most famous schools in Europe” (AT VI, 5; CSM I, 113), it is generally agreed that Descartes’ initial study of mathematics commenced when he was a student at La Fleche. He reports in the Discourse that, when we he was younger, his mathematical studies included some geometrical analysis and algebra (AT VI, 17; CSM I, 119), and he also mentions that he “delighted in mathematics, because of the certainty and self-evidence of its reasonings” (AT VI, 7; CSM I, 114). However, no specific texts or mathematical problems are mentioned in the 1637 autobiographical sketch. Thus, we rely on remarks made in correspondence for the more specific details of Descartes’ study of mathematics at La Fleche, and these remarks strongly suggest that Clavius was a key figure in Descartes’ earliest (perhaps even initial) study of mathematics. For instance, in a letter from March 1646 written by John Pell to Charles Cavendish, we have good reason to believe that ca. 1616, while a student at La Fleche, Descartes read Clavius’s Algebra (1608). Reporting on his meeting with Descartes in Amsterdam earlier that same year, Pell writes in particular that “[Descartes] says he had no other instructor for Algebra than ye reading of Clavy Algebra above 30 years ago” (cited in Sasaki 2003, 47; cf. AT IV, 729–730 and Sasaki 2003, 45–47 for other relevant portions of that letter). Moreover, in a 13 November 1629 letter written to Mersenne, Descartes refers to the second (1589) edition of Clavius’s annotated version of Euclid’s Elements, in which, as noted above, Clavius presents his pointwise construction of the quadratrix and uses the curve to solve the problem of squaring the circle (AT I, 70–71; the portion of the letter that references Clavius is translated in Sasaki (2003), 47). And following Sasaki (2003), it is reasonable to conclude that Descartes was at least aware of Clavius’ textbook Geometria practica (1604), which was included as part of the mathematics curriculum of La Fleche. (See Sasaki 2003, Chapter Two on Clavius’ influence on and inclusion in the mathematics curriculum of Jesuit schools in the early 1600s.)