16. For the unit is the tenth of ten, and ten units make up a decade, which is itself the limit, the settled goal and boundary of units: it is that which terminates the infinity of number; the term and end of units. Again, the triad combined with the decade, and performing a threefold circuit of tens, produces that most natural number, thirty. For as the triad is in respect to units, so is the number thirty in respect to tens.