I fill up bottles of Yellow Gold, Piracetam, Choline citrate, Cissus quadrangularis, Acetyl-L-Carnitine, and Rhodiola rosea all one-by-one capping without a capping mechanism. It's humbling, you should try it.
And I judge weight per cap by guestimating % capacity of a certain fraction of tablespoon, designated by information on the container. Ballpark figures are all that counts, anyway.