Congius

·noun A gallon, or four quarts.

II. Congius ·noun A liquid measure containing about three quarts.

congius
congĭus, ii, m., a Roman measure for liquids, containing the eighth part of an amphora, six sextari...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
congius
congius ī, m a measure for liquids, six sextarii (nearly six pints English): olei, L. ...

An Elementary Latin Dictionary