εἰς πέλαγος σπέρµα βαλεῖν καὶ γράµµατα γράψαι ἀµφότερος µόχθος τε κενὸς καὶ πρᾶξις ἄκαρπος → throwing seeds and writing letters at sea are both a vain and fruitless endeavor
per-dignus: a, um, adj.,
I very worthy; with abl.: homo perdignus tuā amicitiā, Cic. Fam. 13, 6, 4.