The Players by Cezanne.
Hemingway commented frequently on how hunger sharpened his senses. So he would go nearly every day to the Musee du Luxembourg when he couldn't afford to eat to better appreciate the Cezannes.
In "A Moveable Feast", he said he was learning something from the Cezannes that made writing simple true sentences far from enough to make the stories have the dimensions he was tring to put into them. He said he was learning very much, though, from the Cezannes.