If we focus on warheads, then the lightest one in 1959 was the W-25 which weighed between 218 and 221 pounds; however, it had a yield of only 1.7 kilotons (much lower than either Fat Man or Little Boy). Lager yield warheads ranged in weight from about 900 pounds to over 6,000 pounds - the US nuclear bombs were even heavier (the Mk.24 bomb weighed over 40,000 pounds).
That's a LOT of beer!