Originally Posted By: Greger
half-pint, pint, quart, half-gallon, and (rarely) the gallon. The cup was thought to be hardly worth mentioning
A half pint being a cup leads me to believe that the volume of the original "A cup" may well have been a "half pint".

Dang scientits...
“You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.”
– R. Buckminster Fuller