Giorgio Vasari, Lives of the Most Excellent Painters… (1850)
“ Filippo displayed equal art in the Serpent itself, insomuch that the venom, the foetid breath, and the fire, seem rather to be real than merely painted. The invention of the picture, in which the saint is crucified, has also been much commended; the artist would seem to have figured to himself that San Filippo had been fastened to the cross while it lay extended on the earth, and to have been then raised and dragged aloft by means of ropes, cords, and stakes ”
