ORIGINAL: Villa
I may be wrong, but I believe if you throw a standard handkerchief into the prop that the engine stops with no damage, except to the handkerchief. Can you imagine what might have happened if your plane had not been properly restrained? Many people start the engine on the ground, with no restrain. Twice in my 40 years in R/C I have started the engine while it was at full throttle. To me it is a heart stopper. Fortunately, each time the plane was on one of our Engine Starting Safety Stands, so it was well restrained. We have 6 of these stands at our field.
Well, that was a common method we used years ago with smaller engines in my CL days, I don't think I'd try that on anything larger than a 15 size engine. Stopping the prop that way could lead to at the minimum a broken prop,, at worse a bent crank.