Arrian, Discourses of Epictetus
1.2.8-11 (tr. W.A. Oldfather):
 For to one man it is reasonable to hold a chamber-pot for another, since he considers only that, if he does not hold it, he will get a beating and will not get food, whereas, if he does hold it, nothing harsh or painful will be done to him;  but some other man feels that it is not merely unendurable to hold such a pot himself, but even to tolerate another's doing so.  If you ask me, then, "Shall I hold the pot or not?" I will tell you that to get food is of greater value than not to get it, and to be flayed is of greater detriment than not to be; so that if you measure your interests by these standards, go and hold the pot." Yes, but it would be unworthy of me."  That is an additional consideration, which you, and not I, must introduce into the question. For you are the one that knows yourself, how much you are worth in your own eyes and at what price you sell yourself. For different men sell themselves at different prices.
 τῷ γάρ τινι εὔλογον τὸ ἀμίδα παρακρατεῖν αὐτὸ μόνον βλέποντι, ὅτι μὴ παρακρατήσας μὲν πληγὰς λήψεται καὶ τροφὰς οὐ λήψεται, παρακρατήσας δ᾽ οὐ πείσεταί τι τραχὺ ἢ ἀνιαρόν·  ἄλλῳ δέ τινι οὐ μόνον τὸ αὐτὸν παρακρατῆσαι ἀφόρητον δοκεῖ, ἀλλὰ καὶ τὸ ἄλλου παρακρατοῦντος ἀνασχέσθαι.  ἂν οὖν μου πυνθάνῃ "παρακρατήσω τὴν ἀμίδα ἢ μή;", ἐρῶ σοι ὅτι μείζονα ἀξίαν ἔχει τὸ λαβεῖν τροφὰς τοῦ μὴ λαβεῖν καὶ μείζονα ἀπαξίαν τὸ δαρῆναι τοῦ μὴ δαρῆναι· ὥστ᾽ εἰ τούτοις παραμετρεῖς τὰ σαυτοῦ, ἀπελθὼν παρακράτει.  "ἀλλ᾽ οὐκ ἂν κατ᾽ ἐμέ." τοῦτο σὲ δεῖ συνεισφέρειν εἰς τὴν σκέψιν, οὐκ ἐμέ. σὺ γὰρ εἶ ὁ σαυτὸν εἰδώς, πόσου ἄξιος εἶ σεαυτῷ καὶ πόσου σεαυτὸν πιπράσκεις· ἄλλοι γὰρ ἄλλων πιπράσκουσιν.
The slave in charge of holding the chamber-pot was the λασανοφόρος