The Pope sent a messenger asking Giotto to send him back a small picture . Instead of doing a painting , which would take many days , Giotto drew , in red paint , a circle that was so perfect that it seemed as though it was drawn using a pair of compasses . Vasari also relates that when the Pope sent a messenger to Giotto , asking him to send a drawing to demonstrate his skill , Giotto drew , in red paint , a circle so perfect that it seemed as though it was drawn using a compass and instructed the messenger to give that to the Pope .