Serious question?

Is a gill an eighth or a quarter of a pint or of a (litre) bottle?  Either way, making whisky butter for mince pies and Xmas pud. requires two people:  the first must keep tasting the mix until they can't taste the whisky any more (either the brain or the olfactory nerves get paralysed) and the second person must then bring fresh taste buds into play for the final say as to whether 'enough' has been attained