Cavendish rings a bell. And while GR/space-time distortions may work, I don't know more about it than like a single diagram and analogy of marbles on a rubber sheet thing. Certainly they didn't thing about it back then. The classical formula works very well, and I seem to remember Kepler having three laws of motion that were explained by maybe newton using calculus and the one classic gravity formula, but am very very hazy on details and timing