How to check lawn mower oil level without a dipstick?

It's pretty near impossible to overfill a small engine such as is on a lawn mower with oil. There is no oil pump to circulate the oil, so the only manner of lubrication the piston, rings, pin, crankshaft, etc. have is a splash method of distribution. Fill the pan till the oil is up to the threads of the plug hole and call it good. Temp. makes no difference at all.