Yes. If you could measure down to 0.001 pounds and stood there, without respiration, food, or sweating for the experiment. Another option would be to get a very large scale, - the more sensitive the better - and find something very close to max weight there too. Think a 2 ton scale that might go down to 0.1 or even 0.01 pounds, and putting just under 2 tons on it. I have no idea if such things exist or how much they would cost, but it would be a lot. A big balloon of water suspended on a tree might work on a still day, but any variables such as wind or animals might cause weird readings. I don't know what could be done with standard household equipment. Load cells are pretty good devices. they convert forces (loads) into electrical signals which can then be measured. This is how all digital scales work. The key to a good load cell measurement is to get the proper range, and sensitivity, along with electronic conditioning (amplification and filtering) to make the output workable for your situation. People are notoriously bad experiment subjects as everything we do - including movement - typically affects the readings. Better to use a solid object on a "step on" scale, and anything that can be done with suspension is usually good with water, since it is readily available and relatively heavy. I might do the calculations to see how much of an impact the moon has on weight, but I don't suspect it is much on the whole.