In 1907, Einstein described a "Gedankenexperiment" in which he showed that free fall in a gravitational field is indistinguishable from a body at rest in an elevator accelerated upwards in zero gravity. This paper describes an apparatus, which is simple to make and simple to operate, that acts as an observable footnote to Einstein's example. It also includes an examination of acceleration-dependent forces as well as a discussion of those frames of reference in which Newton's laws of classical mechanics are not valid. (Contains 1 figure.)