Titus Livius (Livy), The History of Rome, Book 5
D. Spillan, A.M., M.D., Ed.

15. In the mean time many prodigies were announced; the greater part of which were little credited or even slighted, because individuals were the reporters of them, and also because, the Etrurians being now at war with them, they had no aruspices through whom they might attend to them. [2] The attention of all was turned to a particular one: the lake in the Alban grove swelled to an unusual height without any rain, or any other cause which could account for the matter independently of a miracle. [3] Commissioners were sent to the Delphic oracle to inquire what the gods portended by this prodigy; [4] but an interpreter of the fates was presented to them nearer home in a certain aged Veientian, who, amid the scoffs thrown out by the Roman and Etrurian soldiers from the out-posts and guards, declared, after the manner of one delivering a prophecy, that until the water should be discharged from the Alban lake, the Romans should never become masters of Veii. [5] This was disregarded at first as having been thrown out at random, afterwards it began to be canvassed in conversation; until one of the Roman soldiers on guard asked one of the townsmen who was nearest him (a conversational intercourse having now taken place in consequence of the long continuance of the war) who he was, who threw out those dark expressions concerning the Alban lake? [6] After he heard that he was an aruspex, being a man whose mind was not without a tincture of religion, pretending that he wished to consult him on the expiation of a private portent, if he could aid him, he enticed the prophet to a conference. [7] And when, being unarmed, they had proceeded a considerable distance from their respective parties without any apprehension, the Roman youth having the advantage in strength, took up the feeble old man in the sight of all, and amid the ineffectual bustle made by the Etrurians, carried him away to [p. 342]his own party. [8] When he was conducted before the general, and sent from thence to Rome to the senate, to those who asked him what that was which he had stated [9??] concerning the Alban lake, he replied, “that undoubtedly the gods were angry with the Veientian people on that day, on which they had inspired him with the resolve to disclose the ruin of his country as destined by the fates. [10] Wherefore what he then declared urged by divine inspiration, he neither could recall so that it may be unsaid; and perhaps by concealing what the immortal gods wished to be published, no less guilt was contracted than by openly declaring what ought to be concealed. [11] Thus therefore it was recorded in the books of the fates, thus in the Etrurian doctrine, that whensoever the Alban water should rise to a great height, then, if the Romans should discharge it in a proper manner, victory was granted them over the Veientians: before that occurred, that the gods would not desert the walls of Veii.” [12] He then detailed what would be the legitimate method of draining. But the senate deeming his authority as but of little weight, and not to be entirely depended on in so important a matter, determined to wait for the deputies and the responses of the Pythian oracle.