Pythagoras is believed to have received his ancient wisdom from the Delphi Oracle, Δελφοί or Pythia. A secret order who's rituals are still unknown to this day, sworn to secrecy deeper than the freemasons even (you can read their rites on Amazon).

All we do know is the sacred rites involved removing an item or items from a closed box, and then after placing them into a basket.
Also they were given a magnetized ring for the finger.
And not much else is known...except for what Pythagoras did.

Pythagoras went to ancient Egypt and visited the pyramids, learning much applying A2 + B2 = C2 to the ...shall we call it a visible brightly lit object that can be seen from other planets and locked onto for strong high torgue sheering quantum entanglement transfer (4 sided base triangle pyramid with a bright white reflective cap).
Or, the art of mathematics.
Addition.
Ratio.
Comparing one measured observation amount of base building block cubes, to another unknown amount, adding them together and subtracting the difference.
Over and over.
And calling it by differing names.