Music
- Aristotle, Metaphysics, Book XIV, 1090a20-5: "The Pythagoreans, on the other hand, observing that many attributes of numbers apply to sensible..."
- Vitruvius, De Architectura, Book I, Chapter I, Paragraphs 1-3: "The architect should be equipped with knowledge of many branches of study and varied kinds..."
- Vitruvius, De Architectura, Book V, Chapter V, Paragraphs 1-3: Plan of the Theatre: "The plan of the theatre itself is to be constructed as follows. Having fixed upon..."
- Iamblichus, Life of Pythagoras, P. 80. I swear by him who the tetractys found.: "The tetrad was called by the Pythagoreans every number, because it comprehends in itself all..."