De E apud Delphos

Now the generation of this number, which has so many and so great faculties, is also beautiful,—not that which we have already discoursed of, from two and three, but that which the first principle joined with the first square has exhibited. For the principle of all number is unity, and the first square is the quaternary; now the quinary is composed of these, as of form and of matter which has attained to perfection. And if it is right, which some hold, that unity is also square, as being the power of itself and terminating in itself; the quinary, being made of the first two squares, could not have a more noble original.