A quote of a quote from page 22 of The First 20 Hours: How to Learn Anything . . . Fast!. The original is from, Art & Fear: Observations on the Perils (and Rewards) of Artmaking.
The ceramics teacher announced on opening day that he was dividing the class into two groups. All those on the left side of the studio, he said, would be graded solely on the quantity of work they produced, all those on the right solely on its quality.
His procedure was simple: on the final day of class he would bring in his bathroom scales and weigh the work of the "quantity" group: fifty pounds of pots rated an A, forty pounds a B, and so on. Those being graded on "quality," however, needed to produce only one pot - albeit a perfect one- to get an A.
Well, come grading time a curious fact emerged: the works of the highest quality were all produced by the group being graded for quantity. It seems that while the "quantity" group was busily churning out piles of work and learning from their mistakes, the "quality" group had sat theorizing about perfection, and in the end had little more to show for their efforts than grandiose theories and a pile of dead clay.