@Reconstructo,
But the reason these ancients seem 'mystical' might simply be, because 'the mystical' is actually a much deeper, or bigger, view of reality than ordinary people (the hoi polloi - that's us!) have. (I don't think there was anything wrong with your tone incidentally, I am just waxing poetic here.)
One of the themes I am working on is the 'transformation of perception'. When we look, what are the eyes through which we see? As you keep saying, rightly, we are seeing through a mesh of concepts, perceptual constructs and the like. (In Sanskrit, vijnana, or conceptual constructions.)
As Blake said:- "if the doors of perception were cleansed, we would see everything as it is: infinite" (one of the founding phrases of the psychedelic era, and the source for the name of the band, The Doors.) Now I think the pythagorean vision is transformational in this sense. It requires its adherents to 'see differently'. Certainly his is a spiritual/religious vision, and pythagoras a deeply religious figure, but again diifferently to the sense that this is understood in today's world. It is the fact that he is kind of theosophical, but also with his scientific leanings, which make him so fascinating. Archimedes was one of his lineage, and was similarlly a kind of 'mathematical sage' (and genius!).
Anyway, I don't really have a point here, I will do some more reading of the Pythagorean Sourcebook tonight and maybe come up with some more passages. I am just expressing General Enthusiasm.:bigsmile: