Achille Marozzo - On mastery
"I want you to know that it is a beautiful mystery to know how to teach people well, more than to just play; for a man, if he knows how to play well and does not know how to teach, is not good (he is single): but one that knows how to teach well, is good for many people; and know that when he knows the one and the other, he is of double virtue and is a double master." Achille Marozzo "A new work" 1536