The Collaborative International Dictionary of English v.0.48:

As \As\, n.; pl. Asses. [L. as. See Ace.]
   1. A Roman weight, answering to the libra or pound, equal to
      nearly eleven ounces Troy weight. It was divided into
      twelve ounces.
      [1913 Webster]

   2. A Roman copper coin, originally of a pound weight (12
      oz.); but reduced, after the first Punic war, to two
      ounces; in the second Punic war, to one ounce; and
      afterwards to half an ounce.
      [1913 Webster]