This paper describes a new piece of apparatus for obtaining an accurate table of time and distance of a freely falling body; by the use of counterweights, the device serves as an accurate Atwood machine to check Newton’s Second Law of Motion.
PETER L. TEA, "FREE FALL APPARATUS, NEWTON’S SECOND LAW OF MOTION," J. Opt. Soc. Am. 17, 138-138 (1928)