Possible Clues:

• That old Greek might have helped you to figure out a hidden clue before I did
• Rod raised hat - he was a mathematician
• Ancient Greek master of geometry
• 'Elements' author
• Cleveland avenue said to have America's first traffic light, 1914
• Geometrician I'd clue in another way
• Old Greek master of geometry
• Might he help you figure out the twisted clue I had?
• Early Greek geometrician
• Alexandrian mathematician