Passage 9.38.2
ἔστι δέ σφισι καὶ κρήνη θέας ἀξία· καταβαίνουσι δὲ ἐς αὐτὴν ὕδωρ οἴσοντες. θησαυρὸς δὲ ὁ Μινύου, θαῦμα ὂν τῶν ἐν Ἑλλάδι αὐτῇ καὶ τῶν ἑτέρωθι οὐδενὸς ὕστερον, πεποίηται τρόπον τοιόνδε· λίθου μὲν εἴργασται, σχῆμα δὲ περιφερές ἐστιν αὐτῷ, κορυφὴ δὲ οὐκ ἐς ἄγαν ὀξὺ ἀνηγμένη· τὸν δὲ ἀνωτάτω τῶν λίθων φασὶν ἁρμονίαν παντὶ εἶναι τῷ οἰκοδομήματι.
They also have a spring worthy of note, to which they descend in order to draw water. The treasury of Minyas, a marvel among the sights of Greece itself and not inferior to any elsewhere, is constructed in the following manner. It is built of stone, and its shape is round, its roof rising to a height not excessively pointed. They say that the topmost stone serves as a keystone binding the entire structure together.