What is heft?
Hefting, historically, was manually assessing the weight of the hive, by checking how heavy it was to lift each side of the hive just clear of the ground, and thus estimate the remaining stores, usually in late winter.
Lots of ways to do it absolutely, these days. No need for the experience of the operator as was usual in years gone by. There are still a lot out there who do not waste time with mechanical aids, or the accuracy of a load cell, so it still does not need to be a 'rocket science' project.
That said use of 'electronic digital travel case' scales (a fiver from epay?) or use of a lever to reduce the effort is easy enough to arrange. There is no need to dismantle any hives these days to get an accurate measure of it's weight.
So returning to the question - assessing stores from the weight of the hive is a good an answer as necessary.
Regards, RAB