WRONG FT! wrong Gduck! Energy equals mass times the speed of light squared. If it only an energy exchange (and there is no such thing in physics and an 1:1 exchange) then it would be trues but if work is done there is some miniscule mass lost as heat to the universe. That or rewrite the physics books. Well, maybe you have a point. They are always rewriting physics books. Look in any college bookstore! The trend is always toward the debit side of the ledger in compliance with the 2nd Law of Thermodynamics. If you see the universe as closed (finite) then you might have an argument.

Gee, Chongo, you omitted the real work of getting your fingers into that controlling position. I would imagine quite a bit of mass might be lost by one or the other or both parties involved.