Diodorus Siculus 2.57.4-5, summarizing Iambulus' account of the Islands of the Sun (tr. C.H. Oldfather):
 And the inhabitants, they tell us, are extremely long-lived, living even to the age of one hundred and fifty years, and experiencing for the most part no illness.  Anyone also among them who has become crippled or suffers, in general, from any physical infirmity is forced by them, in accordance with an inexorable law, to remove himself from life. And there is also a law among them that they should live only for a stipulated number of years, and that at the completion of this period they should make away with themselves of their own accord, by a strange manner of death; for there grows among them a plant of a peculiar nature, and whenever a man lies down upon it, imperceptibly and gently he falls asleep and dies.
 πολυχρονίους δ᾽ εἶναι τοὺς ἀνθρώπους καθ᾽ ὑπερβολήν, ὡς ἂν ἄχρι τῶν πεντήκοντα καὶ ἑκατὸν ἐτῶν ζῶντας καὶ γινομένους ἀνόσους κατὰ τὸ πλεῖστον.  τὸν δὲ πηρωθέντα ἢ καθόλου τι ἐλάττωμα ἔχοντα ἐν τῷ σώματι μεθιστάνειν ἑαυτὸν ἐκ τοῦ ζῆν ἀναγκάζουσι κατά τινα νόμον ἀπότομον. νόμιμον δ᾽ αὐτοῖς ἐστι ζῆν ἄχρι ἐτῶν ὡρισμένων, καὶ τὸν χρόνον τοῦτον ἐκπληρώσαντας ἑκουσίως μεταλλάττειν ἐξηλλαγμένῳ θανάτῳ· φύεσθαι γὰρ παρ᾽ αὐτοῖς ἰδιοφυῆ βοτάνην, ἐφ᾽ ἧς ὅταν τις κοιμηθῇ, λεληθότως καὶ προσηνῶς εἰς ὕπνον κατενεχθεὶς ἀποθνήσκει.
Diodorus Siculus 3.33.5-6, on the Trogodytes (tr. C.H. Oldfather):
 Those who can no longer accompany the flocks by reason of old age bind the tail of an ox about their own necks and so put an end to their lives of their own free will; and if a man postpones his death, anyone who wishes has the authority to fasten the noose about his neck, as an act of good-will, and, after admonishing the man, to take his life.  Likewise it is a custom of theirs to remove from life those who have become maimed or are in the grip of incurable diseases; for they consider it to be the greatest disgrace for a man to cling to life when he is unable to accomplish anything worth living for. Consequently, a man can see every Trogodyte sound in body and of vigorous age, since no one of them lives beyond sixty years.
 οἱ δὲ διὰ τὸ γῆρας οὐ δυνάμενοι ταῖς ποίμναις ἀκολουθεῖν βοὸς οὐρᾷ τὸν αὐχένα περισφίγξαντες ἑαυτῶν ἀπολύονται τοῦ ζῆν προθύμως· τοῦ δὲ τὸν θάνατον ἀναβαλλομένου τὴν ἐξουσίαν ὁ βουλόμενος ἔχει τὸν δεσμὸν ὡς ἐπ᾽ εὐνοίᾳ περιθεῖναι καὶ μετὰ νουθετήσεως στερῆσαι τοῦ ζῆν.  ὁμοίως δὲ νόμιμον αὐτοῖς ἐστι τοὺς πηρωθέντας ἢ νόσοις δυσιάτοις συνεχομένους ἐξάγειν ἐκ τοῦ ζῆν· μέγιστον γὰρ τῶν κακῶν ἡγοῦνται τὸ φιλοψυχεῖν τὸν μηδὲν ἄξιον τοῦ ζῆν πράττειν δυνάμενον. διὸ καὶ πάντας μὲν ἰδεῖν ἔστι τοὺς Τρωγλοδύτας ἀρτίους μὲν τοῖς σώμασιν, ἰσχύοντας δ᾽ ἔτι ταῖς ἡλικίαις, ὡς ἂν μηδενὸς ὑπερβάλλοντος τὰ ἑξήκοντα ἔτη.