Tao Te Ching

“Pythagoras changed philosophy into the form of a liberal doctrine, considered its principles in a more exalted manner; and investigated its theorems immaterially and intellectually, invented a treatise of such things as cannot be explained in geometry, and discovered the constitution of the mundane figures.”

— Proclus Lycaeus Πρόκλος ὁ Διάδοχος 412 – 485 CE
"The most influential Ancient Greek philosopher you've never heard of"