A proton weighs ~10^-27 kg, so that's about 100 protons. I sincerely doubt we have masses that are quite that good - especially that which can take a high mass

A proton weighs ~10^-27 kg, so that's about 100 protons. I sincerely doubt we have masses that are quite that good - especially that which can take a high mass item (harddrive) and detect an atomic-scale change without being hideously noisy