An obsolete name for the British Imperial pint (34.678 cubic inches or approximately 568.261 milliliters), used in British medicine and pharmacy during the nineteenth century. The octarius was equal to 1/8 congius (gallon)
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}