Lewis & Short

quartārĭus, ii, m. [quartus].

  1. I. A fourth part, quarter of any measure, esp. of a sextarius, a quartern, gill: sumito bituminis tertiarium, et sulphuris quartarium, Cato, R. R. 95, 1: vini, Liv. 5, 47: mellis, Col. 12, 5, 1: farris, Plin. 18, 3, 3, § 9.
  2. II. A mule-driver, muleteer, who received a fourth part of the profits, Lucil. ap. Fest. p. 258 Müll.