Illustration from a 1601 edition of Isidore of Seville's extant works found on Google books
I quoted an article (B:18 on this list) by the Danish historian of science Jens Høyrup when I was looking for material on medieval Arabic and Latin ideas about mathematical tricks. But the article contained much fascinating material I found no way to use. For example, these quotations by St. Isidore of Seville, reputedly “the most learned man of [the early 7th] century in Latin Europe.”
Knowledge of numbers should not be held in contempt: In many passages of the Holy Scripture it elucidates the mysteries therein contained. Not in vain was it said in the praise of God: You made everything in measure, in number, and in weight.
By number, we are not confounded but instructed. Take away number from everything, and everything perishes. Deprive the world of computation, and it will be seized by total blind ignorance, nor can be distinguished from the other animals the one who does not know how to calculate.
Høyrup calls Isidore the “most cited authority of the Middle Ages next to the Bible.” Although his Etymologies included a book on the quadrivium, I’m afraid I have nothing more to cite (he’s apparently not mentioned at all in the current best-seller entitled Quadrivium). The pace of Latin mathematics picked up a few centuries later. Høyrup’s “case study” of the 13th century mathematician Jordanus de Nemore incidentally provides a rapid survey of what happened then; if that’s what you’re looking for, Høyrup’s article is hard to beat.