Laudator Temporis Acti

Aristophanes, Wealth 817-818 (tr. Alan H. Sommerstein):

[A]nd we don't even wipe our bottoms with stones any more -- we're so spoilt we now always use garlic cloves!

ἀποψώμεσθα δ' οὐ λίθοις ἔτι,
ἀλλὰ σκοροδίοις ὑπὸ τρυφῆς ἑκάστοτε.

Aristophanes, Peace 1224-1230 (tr. Sommerstein):

ARMS-DEALER [displaying a cuirass]: And what, alack, shall I do with this rounded cuirass, a beautiful fit, worth ten minas?
TRYGAEUS: Well, that one won't make a loss for you, anyway. Give me that at cost price. [The dealer hands over the cuirass.] It'll be very convenient to crap in --
ARMS-DEALER: Stop this impudent mockery of my goods!
TRYGAEUS [who has placed the cuirass on the ground like a chamberpot and is squatting on it]: -- like this, if you put three stones beside it. Isn't that clever?

Θωρακοπώλης
τί δαὶ δεκάμνῳ τῷδε θώρηκος κύτει
ἐνημμένῳ κάλλιστα χρήσομαι τάλας;
Τρυγαῖος
οὗτος μὲν οὐ μή σοι ποιήσει ζημίαν.
ἀλλ᾽ αἶρέ μοι τοῦτόν γε τῆς ἰσωνίας·
ἐναποπατεῖν γάρ ἐστ᾽ ἐπιτήδειος πάνυ--
Θωρακοπώλης
παῦσαί μ᾽ ὑβρίζων τοῖς ἐμοῖσι χρήμασιν.
Τρυγαῖος
ὡδὶ παραθέντι τρεῖς λίθους. οὐ δεξιῶς;

The scholiast on Aristophanes, Peace 1230, refers to a proverb:

Three stones are enough to wipe one's arse.

τρεῖς εἰσιν ἱκανοὶ πρωκτὸν ἀπομάξαι λίθοι.

This proverb is similar to an instruction in the Islamic tradition, from the hadith Sallallaahu alayhi wasallam:

If any of you goes to defecate, he should take with him three stones, for they will be sufficient for him.

Machon, quoted by Athenaeus 13.578 e (tr. C.B. Gulick):

Now it seems, as is reported, that Mania suffered from the stone; but Gnathaena, because she soiled the bedclothes, was chastised somehow for this by Diphilus. And once after Gnathaena was reviling Mania and said "How about this, sister, even if you did have a stone?" Mania retorted, "I should have given it to you, you wretch, that you might have had something with which to cleanse yourself."

Ἐδόκει δὲ λιθιᾶν, ὡς ἔοιχ', ἡ Μανία·
Γνάθαινα δ'εἰς τὰ στρώμαθ' ὅτι προίετο,
ἐνουθετήθη τοῦτό πως ὑπὸ Διφίλου.
μετὰ ταῦτα δ' ἡ Γνάθαινα πρὸς τὴν Μανίαν
ἐλοιδορεῖτο καὶ λέγει "τί τοῦτο, παῖ,
εἰ καὶ λίθον εἶχες;" ὑπολαβοῦσ' ἡ Μανία
"ἔδωκ' ἄν, ἵν' εἶχες, φήσ', ἀποψᾶσθαι, τάλαν."

Lyncaeus, quoted by Athenaeus 13.584 c (tr. Gulick) tells a similar story, with Phrynê replacing Mania:

Once Phrynê said rather sourly to her, "Suppose you had the stone?" She retorted, "I'd have given it to you to wipe yourself with." For it so happened that one of them had the stone, while the other was suffering from diarrhoea.

Φρύνης δὲ πικρότερον εἰπούσης αὐτῇ "εἱ δὲ λίθον, έφη, εἶχες," "ἀποψήσασθαι ἄν σοι ἔδωκα." ἐτύγχανεν δὲ ἣ μὲν αἰτίαν ἐχουσα λιθιᾶν, ἣ δὲ κοιλίαν προπετεστέραν ἔχειν.