Hippasus

Hippasus of Metapontum was a Greek philosopher and early follower of Pythagoras, active around 530-450 BC. He's sometimes credited with discovering irrational numbers, a finding that would have shattered the Pythagorean belief that all numbers could be expressed as ratios. Ancient sources say he drowned at sea, supposedly as divine punishment - though they disagree on the offense. Some claim he revealed the secret of irrationals and took credit instead of attributing it to Pythagoras, as was customary in the sect. Others say his crime was showing how to fit a dodecahedron inside a sphere. No ancient writer definitively ties him to the discovery of irrationality, and almost nothing else about his life or thought survives.