Giorgio Vasari, Lives of the Most Excellent Painters… (1850)
“ When Duccio ultimately died, what relations, disciples, or property he left, are circumstances alike unknown, but the fact that he bequeathed the invention of “chiaro-scuro” pictures in marble, as a legacy to the art of painting, would of itself be sufficient to secure him infinite praise and glory; he must assuredly be numbered among those benefactors who have adorned our art and promoted its progress ”
