Plutarch, Life of Aristides
21.2-5 (tr. Ian Scott-Kilvert):
 These proposals were ratified, and the Plataeans undertook to offer up a sacrifice to the dead every year in honour of those Greeks who had fallen in battle and were buried on the field, and this ceremony they still carry out to this day in the following manner. On the sixteenth day of the month Maimacterion, which is the Boeotian Alalcomenius, they conduct a procession.
 This is led forth at daybreak by a trumpeter who sounds the charge: after him come waggons full of myrtle leaves and garlands, and then a black bull. These are followed by young men of free birth who carry libations of wine and milk in jars and pitchers of olive-oil and myrrh, and no slave is allowed to play any part in the ceremony, since the men who are being honoured gave their lives for freedom.
 Last of all comes the chief magistrate of Plataea, who for the rest of his term of office is forbidden to touch iron or to wear clothes of any colour but white, but on this occasion is dressed in a scarlet tunic. He carries aloft an urn from the public record office and proceeds, sword in hand, through the middle of the city to the tombs.
 There with his own hands he takes water from the sacred spring, washes the gravestones, and anoints them with myrrh. Then he slaughters the bull by the funeral pyre, offers prayers to Zeus and to Hermes of the Underworld, and calls upon the brave men who died for Greece to come to the banquet and drink the libations of blood. After this he mixes a bowl of wine and water, drinks and pours a libation from it, saying these words: "I drink to the men who died for the freedom of Greece." These rites have been observed by the Plataeans down to the present day.
 κυρωθέντων δὲ τούτων οἱ Πλαταιεῖς ὑπεδέξαντο τοῖς πεσοῦσι καὶ κειμένοις αὐτόθι τῶν Ἑλλήνων ἐναγίζειν καθ᾽ ἕκαστον ἐνιαυτόν. καὶ τοῦτο μέχρι νῦν δρῶσι τόνδε τὸν τρόπον· τοῦ Μαιμακτηριῶνος μηνός, ὅς ἐστι παρὰ Βοιωτοῖς Ἀλαλκομένιος, τῇ ἕκτῃ ἐπὶ δέκα πέμπουσι πομπήν, ἧς προηγεῖται μὲν ἅμ᾽ ἡμέρᾳ σαλπιγκτὴς ἐγκελευόμενος τὸ πολεμικόν,
 ἕπονται δ᾽ ἅμαξαι μυρρίνης μεσταὶ καὶ στεφανωμάτων καὶ μέλας ταῦρος καὶ χοὰς οἴνου καὶ γάλακτος ἐν ἀμφορεῦσιν ἐλαίου τε καὶ μύρου κρωσσοὺς νεανίσκοι κομίζοντες ἐλεύθεροι· δούλῳ γὰρ οὐδενὸς ἔξεστι τῶν περὶ τὴν διακονίαν ἐκείνην προσάψασθαι διὰ τὸ τοὺς ἄνδρας ἀποθανεῖν ὑπὲρ ἐλευθερίας·
 ἐπὶ πᾶσι δὲ τῶν Πλαταιέων ὁ ἄρχων, ᾧ τὸν ἄλλον χρόνον οὔτε σιδήρου θιγεῖν ἔξεστιν οὔθ᾽ ἑτέραν ἐσθῆτα πλὴν λευκῆς ἀναλαβεῖν, τότε χιτῶνα φοινικοῦν ἐνδεδυκὼς ἀράμενός τε ὑδρίαν ἀπὸ τοῦ γραμματοφυλακίου ξιφήρης ἐπὶ τοὺς τάφους προάγει διὰ μέσης τῆς πόλεως.
 εἶτα λαβὼν ὕδωρ ἀπὸ τῆς κρήνης αὐτὸς ἀπολούει τε τὰς στήλας καὶ μύρῳ χρίει, καὶ τὸν ταῦρον εἰς τὴν πυρὰν σφάξας καὶ κατευξάμενος Διῒ καὶ Ἑρμῇ χθονίῳ παρακαλεῖ τοὺς ἀγαθοὺς ἄνδρας τοὺς ὑπὲρ τῆς Ἑλλάδος ἀποθανόντας ἐπὶ τὸ δεῖπνον καὶ τὴν αἱμοκουρίαν. ἔπειτα κρατῆρα κεράσας οἴνου καὶ χεάμενος ἐπιλέγει· "προπίνω τοῖς ἀνδράσι τοῖς ὑπὲρ τῆς ἐλευθερίας τῶν Ἑλλήνων ἀποθανοῦσι." ταῦτα μὲν οὖν ἔτι καὶ νῦν διαφυλάττουσιν οἱ Πλαταεῖς.
Some observations, none of them original:
- Plutarch's account has the ring of eyewitness testimony. He was a Boeotian, from Chaeronea, and could easily have seen this ceremony. Walter Burkert, Homo Necans: The Anthropology of Ancient Greek Sacrificial Ritual and Myth, tr. Peter Bing (Berkeley: University of California Press, 1983), p. 56, and Peter Green, The Greco-Persian Wars (Berkeley: University of California Press, 1996), p. 275.
- The bull is black because black victims are sacrificed to subterranean powers.
- On the iron taboo see J.G. Frazer, The Golden Bough, 3rd ed., Part II: Taboo and the Perils of the Soul (London: Macmillan and Co., Limited, 1911), pp. 225-236.
- According to Liddell-Scott-Jones, the word used by Plutarch here for libation of blood (αἱμοκουρία, var. αἱμακουρία) is a Boeotian word. Pindar also uses it (Olympian Odes 1.90).
- The Battle of Plataea took place in 479 B.C., and so these rites had been performed annually for over 500 years before Plutarch's time.
Related post: The Thirsty Dead