According to Yu A. Lyubimov, Coulomb's main
experiment which involved the torsion balance
had produced some never-before-seen results in his time:
"[Coulomb] had obtained some remarkable results by using the torsion balance method:
laws of attraction adn repulsion, the electrom point charges, magnetic poles,
distribution of electricity on the ground surface of charged bodies and others."
Here is a video demonstrating Coulomb's experiment
in detail and how he obtained his calculations.
The Torsion Balance
The torsion balance apparatus contains several parts but is relatively
easy to replicate in order to reproduce Coulomb's experiment.
The top of the balance is a suspension head which is attached to a fiber that
hangs through a column and hangs inside a lower glass cylinder. On this cylinder
a paper scale marks the angular position. One of the charges is placed on a small
conducting sphere that is able to transfer its charge through an opening at the
top of the lower glass cylinder. The second charge is on a second conducting
sphere placed inside the lower glass cylinder and is suspended from the fiber
at a balanced crossbar.