Laudator Temporis Acti

Aelian, Characteristics of Animals 6.51 (tr. A.F. Scholfield):

It is said that Prometheus stole fire, and the story goes that Zeus was angered and bestowed upon those who laid information of the theft a drug to ward off old age. So they took it, as I am informed, and placed it upon an ass. The ass proceeded with the load on its back; and it was summer time, and the ass came thirsting to a spring in its need for a drink. Now the snake which was guarding the spring tried to prevent it and force it back, and the ass in torment gave it as the price of the loving-cup the drug that it happened to be carrying. And so there was an exchange of gifts: the ass got his drink and the snake sloughed his old age, receiving in addition, so the story goes, the ass's thirst.

τὸν Προμηθέα κλέψαι τὸ πῦρ ἡ φήμη φησί, καὶ τὸν Δία ἀγανακτῆσαι ὁ μῦθος λέγει καὶ τοῖς καταμηνύσασι τὴν κλοπὴν δοῦναι φάρμακον γήρως ἀμυντήριον. τοῦτο οὖν ἐπὶ ὄνῳ θεῖναι τοὺς λαβόντας πέπυσμαι. καὶ τὸν μὲν προϊέναι τὸ ἄχθος φέροντα, εἶναι δὲ ὥραν θέρειον, καὶ διψῶντα τὸν ὄνον ἐπί τινα κρήνην κατὰ τὴν τοῦ ποτοῦ χρείαν ἐλθεῖν. τὸν οὖν ὄφιν τὸν φυλάττοντα ἀναστέλλειν αὐτὸν καὶ ἀπελαύνειν, καὶ ἐκεῖνον στρεβλούμενον μισθόν οἱ τῆς φιλοτησίας δοῦναι ὅπερ οὖν ἔτυχε φέρων φάρμακον. οὐκοῦν ἀντίδοσις γίνεται, καὶ ὁ μὲν πίνει, ὁ δὲ τὸ γῆρας ἀποδύεται, προσεπιλαβὼν ὡς λόγος τὸ τοῦ ὄνου δίψος.

Nicander, Theriaca 343-358 (tr. A.F. Scholfield):

Now there is a tale of ancient days current among men how, when the first-born seed of Cronus became lord of heaven, he apportioned to his brothers severally their illustrious realms, and in his wisdom bestowed upon mortals Youth, honouring them because they had denounced the Fire-Stealer. The fools, they got no good of their imprudence: for being sluggards and growing weary, they entrusted the gift to an ass for carriage, and the beast, his throat burning with thirst, ran off skittishly, and seeing in its hole the deadly, trailing brute, implored it with fawning speech to aid him in his sore plight. Whereat the snake asked of the foolish creature as a gift the load which he had taken on his back; and the ass refused not its request. Ever since then do trailing reptiles slough their skin in old age, but grievous end attends mortals. The affliction of thirst did the deadly brute receive from the braying ass, and imparts it with its feeble blows.

ὠγύγιος δ' ἄρα μῦθος ἐν αἰζηοῖσι φορεῖται,
ὡς, ὁπότ' οὐρανὸν ἔσχε Κρόνου πρεσβίστατον αἷμα,
Νειμάμενος κασίεσσιν ἑκὰς περικυδέας ἀρχάς        345
Ιδμοσύνῃ, νεότητα γέρας πόρεν ἡμερίοισι
Κυδαίνων· δὴ γάρ ῥα πυρὸς ληίστορ' ἔνιπτον.
Αφρονες· οὐ μὲν τῆς γε κακοφραδίῃς ἀπόνηντο·
Νωθεῖ γὰρ κάμνοντες ἀμορβεύοντο λεπάργῳ
Δῶρα· πολύσκαρθμος δὲ κεκαυμένος αὐχένα δίψῃ        350
Ρώετο, γωλειοῖσι δ' ἰδὼν ὁλκήρεα θῆρα
Οὐλοὸν ἐλλιτάνευε κακῇ ἐπαλαλκέμεν ἄτῃ
Σαίνων· αὐτὰρ ὁ βρῖθος, ὃ δή ῥ' ἀνεδέξατο νώτοις,
ᾔτεεν ἄφρονα δῶρον, ὁ δ' οὐκ ἀπανήνατο χρειώ.
ἐξότε γηραλέον μὲν ἀεὶ φλόον ἑρπετὰ βάλλει        355
ὁλκήρη, θνητοὺς δὲ κακὸν περὶ γῆρας ὀπάζει·
νοῦσον δ' ἀζαλέην βρωμήτορος οὐλομένη θήρ
δέξατο, καί τε τυπῇσιν ἀμυδροτέρῃσιν ἰάπτει.

Note the acrostic showing the poet's name, formed by the letters at the beginning of lines 345-353.

See Malcolm Davies, "The ancient Greeks on why mankind does not live forever," Museum Helveticum 44.2 (1987) 65-75.