Giotto's O

There is a story* that Giotto, when requested to provide evidence of his expertise by Pope Boniface XVIII, stopped what he was doing, dipped a brush into red paint and executed a perfect circle in one stroke. This is the kind of fable that could stop you in your tracks. I began to draw circles in silverpoint, but being imperfect, I continued to draw them right on top of each other and ended up with this: