Lewis & Short

rauduscŭlum (rōd- and rūd-), i, n. dim. [raudus].

  1. I. A little piece of brass used as a coin (an old word): in mancipando cum dicitur: Rudusculo libram ferito, asse tangitur libra, Fest. s. v. rodus, p. 265 Müll.; v. raudus.
    Hence,
  2. II. Transf., a small sum of money: de raudusculo Numeriano multum te amo, in regard to that little debt of Numerius, Cic. Att. 7, 2, 7: de raudusculo quod scribis, id. ib. 4, 8, a, § 1.