It was a custom with Apelles, to which he most tenaciously adhered, never to let any day pass, however busy he might be, without exercising himself by tracing some outline or other,-a practice which has now passed into a proverb. It was also a practice with him, when he had completed a work, to exhibit it to the view of the passers-by in his studio, while he himself, concealed behind the picture, would listen to the criticisms.... Under these circumstances, they say that he was censured by a shoemaker for having represented the shoes with one latchet too few. The next day, the shoemaker, quite proud at seeing the former error corrected, thanks to his advice, began to criticise the leg; upon which Apelles, full of indignation, popped his head out and reminded him that a shoemaker should give no opinion beyond the shoes, -a piece of advice which has equally passed into a proverbial saying.