My grandfather was quite the baseball player back in the day. One of the top recruits of the 1940's out of Dowling High in Des Moines, he played in the Yankees organization as well as with some of the greatest who ever lived during WW2 exhibition games. He would often boast how he could hit off anyone and I cant remember the number of times he told me that he hit a home run off Satchel Paige.
There was, however, one pitcher that scared the crap out of my cocky ole grandpa, Bob Feller. Probably the greatest player ever to hail from Iowa, Feller was known to have a beast of a fastball and the one time my grandfather faced him in an exhibition game in DSM, he had someone tell Feller that he wanted to see what he had. The cocky young kid would never forget that stand, out after 4 pitches, one up near the head, then 3 strikes down the middle while my gramps head was probably still spinning.
I remember reading once that they had to measure the velocity of Fellers fastball with a motorcycle but could not find that photo, but this video does a pretty good job of conveying the awe his pitches invoked back then, not to mention the great commentary.