Calculations involving feet and inches are sometimes performed by means of duodecimal arithmetic; i.e., in effect, the tables of square measure and of cubic measure are amplified by the insertion of intermediate units.
For square measure 12 square inches = I superficial prime, 12 superficial primes = I square foot; while for cubic measure 12 cubic inches = I solid second, 12 solid seconds = I solid prime, 12 solid primes = I cubic foot.
Though Queipo has opposed this connexion (not noticing the Greek link of the digit), he agrees that it is supported by the Egyptian square measure of the plethron, being equal to the Roman actus (33).