Another fun fact is that UK gallons are based on the volume occupied by ten pounds of water. Combined with the fact there's 20 ounces in UK pint this means a fluid ounce of water weighs an ounce, and a pint of water weighs a pound and a quarter.

Not that you're very likely to encounter British fluid ounces any more, the smallest imperial unit of volume I generally run into is the half-pint.

Yeah. It'd've been neat if the US gallon was defined to be 256in^3 (with the US in being exactly 2.5cm). Then, it'd be exactly 4000 cm^3 (4L) to a US gallon, and the table of "prefixes" would be:

    gallon      2^0

    half-gallon 2^-1
    quart       2^-2
    pint        2^-3
    cup         2^-4
    gill        2^-5
    jill        2^-6    -- invented half-gill
    ounce       2^-7
    tbsp        2^-8
    half-tbsp   2^-9
    dram        2^-10

    peck        2^1
    half-bushel 2^2
    bushel      2^3
    half-barrel 2^4
    barrel      2^5
    hogshead    2^6
    ???         2^7
    ???         2^8