Lewis & Short

pūmex, ĭcis, m. (fem., Cat. 1, 2).

  1. I. Lit., a pumice-stone, Plin. 36, 21, 42, § 154; used for smoothing books, Cat. 1, 2; 22, 6; Hor. Ep. 1, 20, 2; Ov. Tr. 1, 1, 11; Mart. 8, 72, 2; hence poet., of verses carefully smoothed, i. e. polished, Prop. 3 (4), 1, 8; used by the effeminate for smoothing the skin, Ov. A. A. 1, 506; Mart. 14, 205; Juv. 8, 16.
    Prov.: aquam a pumice postulare, to try to draw blood from a stone, i. e. to demand money from one who has none, Plaut. Pers. 1, 1, 42; cf. as an image of dryness: pumex non aeque est aridus atque hic est senex, id. Aul. 2, 4, 8.
  2. II. Poet., transf., soft stone, porous rock of any kind, Ov. M. 3, 159; 8, 561; id. F. 2, 315; Verg. G. 4, 44; id. A. 5, 214.
    1. B. In gen., a rock: quae nunc oppositis debilitat pumicibus mare, Hor. C. 1, 11, 5.