upennmanuscripts:LJS 26 - Algorismus ; Tractatum de sphaeraThis is a treatise on the fundamentals o
upennmanuscripts:LJS 26 - Algorismus ; Tractatum de sphaeraThis is a treatise on the fundamentals of arithmetic (Algorismus), followed by a treatise on cosmography that describes and illustrates the Ptolemaic model of spherical earth divided into climatic zones at the center of the concentric spheres of the universe. The second treatise has marginal notes in the same ink and possibly hand as the text. It was possibly written in Italy, between 1225 and 1275 CE. Click here for additional information, or here for the facsimile. Or here for the video orientation. -- source link