Steamboat Bill, Jr.
This particular stunt was noted for being done without any trickery (and for being botched by the crew at one point; they measured it wrong and missed flattening Buster Keaton's skull by mere inches). It's reported that both the cameraman and director were too scared to watch when the stunt was performed. It's worth noting that Keaton decided a prop wall would not look realistic enough so the wall used in this scene is a real wall built to code and would have easily crushed him.
By Wall That Is Holey