Herodotus 8.45-46 (tr. A.D. Godley):
45. But when he saw the whole Hellespont hidden by his ships, and all the shores and plains of Abydos thronged with men, Xerxes first declared himself happy, and presently he fell a-weeping.
46. Perceiving that, his uncle Artabanus, who in the beginning had spoken his mind freely and counselled Xerxes not to march against Hellas—Artabanus, I say, marking how Xerxes wept, questioned him and said, "What a distance is there, O king, between your acts of this present and a little while ago! Then you declared your happiness, and now you weep." "Ay verily," said Xerxes; "for I was moved to compassion, when I considered the shortness of all human life, seeing that of all this multitude of men not one will be alive a hundred years hence."
45. Ὡς δὲ ὥρα πάντα μὲν τὸν Ἑλλήσποντον ὑπὸ τῶν νεῶν ἀποκεκρυμμένον, πάσας δὲ τὰς ἀκτὰς καὶ τὰ Ἀβυδηνῶν πεδία ἐπίπλεα ἀνθρώπων, ἐνθαῦτα ὁ Ξέρξης ἑωυτὸν ἐμακάρισε, μετὰ δὲ τοῦτο ἐδάκρυσε.
46. Μαθὼν δέ μιν Ἀρτάβανος ὁ πάτρως, ὃς τὸ πρῶτον γνώμην ἀπεδέξατο ἐλευθέρως οὐ συμβουλεύων Ξέρξῃ στρατεύεσθαι ἐπὶ τὴν Ἑλλάδα, οὗτος ὡνὴρ φρασθεὶς Ξέρξην δακρύσαντα εἴρετο τάδε. "Ὦ βασιλεῦ, ὡς πολλὸν ἀλλήλων κεχωρισμένα ἐργάσαο νῦν τε καὶ ὀλίγῳ πρότερον· μακαρίσας γὰρ σεωυτὸν δακρύεις." ὃ δὲ εἶπε "Ἐσῆλθε γάρ με λογισάμενον κατοικτεῖραι ὡς βραχὺς εἴη ὁ πᾶς ἀνθρώπινος βίος, εἰ τούτων γε ἐόντων τοσούτων οὐδεὶς ἐς ἑκατοστὸν ἔτος περιέσται."
St. Jerome, letter 60.18 (to Heliodorus; tr. F.A. Wright):
That mighty king Xerxes, who overthrew mountains and turned the sea into solid ground, when from his high place he looked upon his infinite multitudes and his countless host of men, is said to have wept at the thought that not one of those whom he saw would in a hundred years be alive. Oh, if we could ascend into such a watch-tower as would give us a view of the whole world spread beneath our feet! Then I would show you a universe in ruins, peoples warring against peoples, and kingdoms shattered on kingdoms. You would see some men being tortured, some killed, others drowned at sea, others dragged off to slavery; here a wedding, there lamentation; some being born, others dying; some living in affluence, others begging their bread; not merely Xerxes’ army, but the inhabitants of the whole world now alive destined soon to pass away. Words fail; for language is inadequate to the greatness of this theme.
Xerxes, ille rex potentissimus, qui subvertit montes, maria constravit, cum de sublimi loco infinitam hominum multitudinem et innumerabilem vidisset exercitum, flesse dicitur, quod post centum annos nullus eorum, quos tunc cernebat, superfuturus esset. O si possemus in talem ascendere speculam, de qua universam terram sub nostris pedibus cerneremus! Iam tibi ostenderem totius mundi ruinas, gentes gentibus et regnis regna conlisa; alios torqueri, alios necari, alios obrui fluctibus, alios ad servitutem trahi; hic nuptias, ibi planctum; illos nasci, istos mori; alios affluere divitiis, alios mendicare; et non Xerxis tantum exercitum, sed totius mundi homines, qui nunc vivunt, in brevi spatio defuturos. Vincitur sermo rei magnitudine et minus est omne quod dicimus.