I remember reading about this in Mason & Dixon. Mason, who worked at the Royal Observatory, was the one who identified this mountain as the best place for the experiment (and was asked to help with it but declined).

IIRC, it was partly the Mason Dixon line that inspired this experiment. They noticed syatematic errors in the line because their plumb bobs were deflected by gravitational pull from local terrain. At the time they speculated it was because of the Alleghenies, though it was probably more localized variations in gravity.