Can I measure torque accurately by an electrical or electronic method?
Fix a lever of a precise known length to the specimen and add calibrated masses. Measure the deflection with a dial gauge.

Perpendicularity might be a concern and could be addressed with geometry... However, the error that introduces is probably small compared to other sources. The sources of errors may well be worth checking. I know that for the dynamometers we used on engines, pumps etc there was no correction but the beam was usually corrected back to a given calibrated zero point.