Perhaps not wanted, but the standard A4, 80g/m² sheet is exactly 5grams (A4 is exactly 1/16 (2⁴) of a square meter). Which puts the 500-sheets ream at exactly 2.5kg.
This said, even in my metric country, we still have fairly poetic sheet sizes.
The “Grand Aigle” being the format of nautical charts produced by our “S.H.O.M.” used to be a major constraint in any sea-going watercraft.