We have no certain paintings by Cennino, and I have always supposed that he must have been quite a bad painter. (There are two reasons for thinking so: first, that he was a third-generation follower of Giotto, and second that he was so much interested in technique that he wrote a book about it.)
— The Materials and Techniques of Medieval Painting by Daniel V. Thompson (Page 54)
Incredible self-own (and dig at Giotto for some reason?)