We see from a statement of Cassiodorus that he furnished manuals for the quadrivium of the schools of the middle ages (the " quattuor matheseos disciplinae," as Boetius calls them) on arithmetic, music, geometry and astronomy.
The senators' calceus had four such straps (quattuor corrigiae), which were wound round the ankle (cf.
His chief work, Doctoris resoluti Joannis Bacconis Anglici Carmelitae radiantissimi opus super quattuor sententiarum libris (published 1510), has passed through several editions.
Thus, corresponding to the Latin quattuor, we find the Oscan petora, the Gaulish petor-ritum, " four-wheeler," the Welsh pedwar, " four," &c., while the Irish cethir, " four," corresponds more closely to the Latin.
These latter were printed in 1496 at Bologna, and entitled Expositio Aurea super totam artemveterem; Quaestiones in quattuor libros sententiarum (Lyons, 1495).