And the unit, and the decade, and the century, and the thousand, are the four boundaries which generate the decade, which last number, besides what has been already said, displays also other differences of numbers, both the first, which is measured by the unit alone, of which an instance is found in the numbers three, or five, or seven; and the square which is the fourth power, which is an equally equal number. Also the cube, which is the eighth power, which is equally equal equally, and also the perfect number, the number six, which is made equal to its component parts, three, and two, and one.