ennead

The ennead, according to the Pythagoreans, circulates all numbers within itself, and there can be no number beyond it. For the natural progression of numbers is as far as to 9, but after it their retrogression takes place. For 10 becomes as it were again the monad. […] Hence it is not possible there should be any elementary number beyond the ennead.

We may assert with confidence that no cycle of this kind, and of equal antiquity or even of inferior antiquity, is the actual existence better attested or more thoroughly authenticated than that of this octaëteris of Philammon of Delphi, or, as we may truly call it, this original Pythian ennead of primitive Hellas.