I was wondering how did Sir Newton measured motion of objects (non celestial ones). What was his toolskit at the time?
The most famous "terrestrial" experiment that I know of was the measurement of the speed of sound in Nevile's Court in Trinity College, Cambridge. As the tour guides will tell you, Newton stomped his foot and listened for the echo from the wall on the opposite end of the North Cloister. He timed the echo by making a (short) pendulum, and adjusting the length until the round trip time of the sound equalled the period (half period?) of the pendulum.
I have not been able to find an authoritative description - but anecdotally I have heard that he actually clapped (or stamped his foot) repeatedly, and either tried to drown the echo with the next clap, or clap rhythmically (so that there is equal time clap-echo-clap-echo). If you were to employ a person with some musical talent (for example, a drummer) to do this, you would then be able to count the number of round trips of sound over a much larger (and more accurately measured) time interval.
The problem with the "really short pendulum" is that inertia of the bob becomes a significant factor - and this will mess up your calculation of the period. Also, a short pendulum is likely to have an angle that not "small" - and when the small angle approximation breaks down, the period of the pendulum no longer follows the simple equation. I suspect that Newton knew that...