ClipArt ETC
"From a cross piece, A, on a stout framework, a heavy block of wood, B, is suspended, in such a way as to move freely backward and forward. A ball fired into this block will drive it back to a distance proportioned to the ball's velocity. All other things being known, the ball's velocity can be discovered." —Quackenbos 1859

Ballistic Pendulum

"From a cross piece, A, on a stout framework, a heavy block of wood, B, is suspended, in such a way…