Pondúsculum, pondúsculi, n. g. pe. cor. Diminutiuum. Colum. A little or smal weight.Cum saxi pondusculo. Colum. With the light weight of a little stone hanged by it.
Lewis and Short: Latin dictionary
ponduscŭlum, i, n.dim. [pondus], a small weight (post-Aug.): saxi, Col. 12, 51: si cooriatur procella, apprehensi pondusculo lapilli (apes) se librant, Plin. 11, 10, 10, 24.