The most accurate scales of the day were jewelers balance scales - but if you measure a diamond to 1.001 carats, it'd be the same in both places as the force on both the diamond and the calibrated weights would both be subject to the same force of gravity.
Just thinking it through...
Written by Bob Koure
Retired software architect, statistical analyst, hotel mgr, bike racer, distance swimmer. Photographer. Amateur historian. Avid reader. Home cook. Never-FBer