De Geometria and other texts
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This collection of mathematical texts was copied by two twelfth-century scribes and annotated by readers in the twelfth century and the fifteenth (or early sixteenth). It includes sections from Pope Sylvester’s Isagoge geometriae, his letter to Adelbold of Utrecht (c. 970-1026) on the area of equilateral triangles with Adelbold’s response, and a short text of less certain authorship on the construction of the planispheric astrolabe (composed of overlaid full discs, as opposed to the quadrant), on display here.The work on the astrolabe exemplifies both the early history of this device in Western Europe and the complementary nature of the seven liberal arts, being placed among texts on geometry. Sylvester was a prominent mathematician before becoming the first French Pope in 999, having studied the trivium at the monastery of St. Gerald in Aurillac and the quadrivium in Spain. Regardless of whether he wrote this particular treatise, he is known to have lectured on the use of the astrolabe, and is likely the first person to have brought this knowledge into Christian Europe. In these regards he resembles the literary figure Geoffrey Chaucer, who also traveled extensively and cultivated an interest in astronomical methods.