I can see keeping a constant weight going to know when 1 pound of water has evaporated from the soil so another pound can be put in. But it seems like a major pain in the ass.
Figure, too, your plant will gain weight.
A little secret, just between us, don't tell anyone... I have a probe I use if I can't tell by weight. Usually, I get that out when the plants are going on flowering and get top heavier.