Passage 10.1.3
τὰ δὲ ἐπιφανέστατα Φωκεῦσίν ἐστιν ἐν κοινῷ· πολέμου γὰρ τοῦ πρὸς Ἰλίῳ μετεσχήκασι, καὶ Θεσσαλῶν ἐναντία ἐπολέμησαν πρότερον ἔτι ἢ ἐλάσαι τὸν Μῆδον ἐπὶ Ἕλληνας, ὅτε δὴ καὶ ἐπεδείξαντο οἱ Φωκεῖς ἔργα ἐς μνήμην. κατὰ γὰρ τὴν Ὑάμπολιν, ᾗ τοὺς Θεσσαλοὺς προσεδέχοντο ἐμβαλεῖν σφισιν ἐς τὴν χώραν, ὑδρίας κεράμου πεποιημένας κατορύξαντες καὶ ἐπʼ αὐτὰς γῆν ἐπιφορήσαντες ὑπέμενον τὴν ἵππον τῶν Θεσσαλῶν· οἱ δέ, ἅτε οὐ προπεπυσμένοι τῶν Φωκέων τὴν τέχνην, ἐπελάσαντες τοὺς ἵππους λανθάνουσιν ἐπὶ τὰς ὑδρίας. ἐνταῦθα ἀπεχωλοῦντο μὲν οἱ ἵπποι τῶν ποδῶν ἐσπιπτόντων σφίσιν ἐς τὰς ὑδρίας, ἐκτείνοντο δὲ καὶ ἀπέπιπτον οἱ ἄνδρες ἀπὸ τῶν ἵππων.
The Phokians' most notable deeds belong to the community as a whole. They took part in the war against Ilium and also fought against the Thessalians even before the invasion of Greece by the Mede, displaying on this occasion exploits worthy of remembrance. For at Hyampolis, where they expected the Thessalians to invade their territory, the Phokians buried jars of clay in the ground, covered them over with earth, and awaited the Thessalian cavalry. The Thessalians, unaware of this device of the Phokians due to no prior warning, drove their horses unwittingly onto these hidden jars. Thereupon, as the horses' feet plunged into the jars, the animals became lame, and their riders fell off and were thrown down from their mounts.