For one may almost say that the whole infinity of numbers is measured by this one, because the boundaries which make it up are four, namely, one, two, three, and four; and an equal number of boundaries, corresponding to them in equal proportions, make up the number of a hundred out of decades; for ten, and twenty, and thirty, and forty produce a hundred. And in the same way one may produce the number of a thousand from hundreds, and that of a myriad from thousands.