One of the really interesting exercises in Arithmetic for Masons is the building of Magic Squares. They show up in the work of Durer and play a role in Dan Brown’s book, The Lost Symbol. This is an exceptional explanation of how to construct a Magic Square as well as a discussion of their use in making a cipher and also of Brother Benjamin Franklin’s magic square. It turns out Franklin’s does not truly qualify as a magic square, but is noteworthy none-the-less.
You may wish to play it at an increased speed if you find the speaker’s cadence a little slow for your ear.