Lewis & Short

sextans, antis, m. [sex].

  1. I. A sixth part of an as (v. as): sextans ab eo quod sexta pars assis, ut quadrans quod quarta et triens quod tertia pars, Varr. L. L. 5, § 171 Müll.: heredes in sextante, Cic. Fam. 13, 29, 4: ex sextante heres institutus, Dig. 44, 2, 30; Cod. Th. 9, 42, 8 pr.
    1. B. In partic.
      1. 1. As a coin: extulit eum plebs sextantibus collatis in capita, Liv. 2, 33 fin.; Plin. 33, 10, 48, § 138; hence, servus sextantis, i. e. of very trifling value, worthless, Laber. ap. Gell. 16, 9, 4.
      2. 2. In weighing, Plin. 26, 11, 74, § 121; Ov. Med. Fac. 65; Mart. 8, 71, 9; (with pondo) Scrib. Larg. 4; 42 al.
      3. 3. As a measure of land, the sixth part of a juger, Varr. R. R. 1, 10, 2; Col. 5, 1, 10.
      4. 4. As a liquid measure, the sixth part of a sextarius, or two cyathi, Col. 12, 23, 1; Mart. 5, 64, 1; Suet. Aug. 77.
      5. 5. As a lineal measure, Plin. 13, 15, 29, § 94.
  2. II. Among mathematicians, the sixth part of the number six, as of the numerus perfectus (v. as), i. e. unity, one, Vitr. 3, 1, 6.