Sextus Empiricus Pyrrhoniae Hypotyposes 3.20.152

[152] Thus, for example, the School of Pythagoras declare that numbers are also elements of the Universe. They assert, in fact, that phenomena are constructed from something, and that the elements must be simple; therefore the elements are non-evident. But of things non-evident, some are corporeal, like atoms and masses, others incorporeal, like figures ¹ and forms and numbers. Of these the corporeal are composite, being constructed from length and breadth and depth and solidity, or even weight. The elements, therefore, are not only non- evident but also incorporeal.