Titus Livius (Livy), The History of Rome, Book 5
Benjamin Oliver Foster, Ph.D., Ed.

15. Meanwhile many portents were reported, most of which, because they had only one witness each to vouch for them, obtained no credence and were slighted; and, besides, when the Etruscans, whose services they employed to avert evil omens, were at war with them, they had no soothsayers. [2] One thing occasioned universal anxiety, namely that the lake in the Alban Wood, without any rains or other cause to make it less than a miracle, rose to an unwonted height. [3] To inquire what the gods could possibly foretell by that prodigy, envoys were sent to the Delphic oracle. [4] But a nearer interpreter of the fates presented himself, an old man of Veii, who, while the Roman and Etruscan soldiers were scoffing at one another as they stood guard at the outposts, declared in a prophetic strain that until the water should be drawn off from the Alban Lake the Romans never could take Veii. [5] At first they made light of this as an idle taunt; then they began to talk it over; presently one of the Roman outpost inquired of the townsman nearest him (for owing to the long continuance of the war they had now got into the way of conversing together) who that man was who threw out mysterious hints regarding the Alban Lake. [6] When he heard that he was a soothsayer, being himself not without a touch of [p. 55]superstition, he alleged a desire to consult him¹ about the averting of a domestic portent, if he could spare the time, and so enticed the seer to a conference. [7] And when they had walked a little way apart from the friends of both, unarmed and fearing nothing, the stalwart young Roman laid hold of the feeble old man in the sight of them all, and despite an unavailing hubbub raised by the Etruscans, bore him off to his own fellows. [8] There they had him before the general, who sent him on to Rome, to the senate. [9] When the Fathers questioned him what it was he had meant about the Alban Lake, he answered that the gods must surely have been incensed at the people of Veii on the day when they put it into his: [10] mind to reveal the destruction destined to befall his native city; and so what he had then uttered under divine inspiration, he could not now unsay and recall; and perhaps in concealing what the immortal gods wished to be published guilt was incurred no less than by disclosing what should be hid. [11] Thus then it was written in the books of fate, thus handed down in the lore of the Etruscans, that when the Alban water should overflow, if then the Romans should duly draw it off, they would be given the victory over the Veientes; until that should come, to pass, the gods would not abandon the walls of Veii. [12] He then went on to explain the appointed method of draining it. But the senators, making slight account of his authority, as not sufficiently trustworthy in so grave a matter, determined to wait for their deputies with the response of the Pythian oracle.²