Titus Livius (Livy), The History of Rome, Book 42
Evan T. Sage, Ph.D. and Alfred C. Schlesinger, Ph.D., Ed.

17. About the same time Gaius Valerius, who had gone to Greece as commissioner to investigate the condition of the region and to enquire into the designs of Perseus,¹ returned from thence, [p. 341]and his reports agreed in all respects with the charges² brought by Eumenes. [2] At the same time, too, he had brought with him Praxo from Delphi, whose house had been the shelter of the assassins, and Lucius Rammius of Brundisium, who was the bearer of the following information. [3] Rammius was a prominent citizen of Brundisium, and he entertained hospitably all Romans, both generals and ambassadors, as well as distinguished personages of foreign states and especially members of princely houses. [4] In consequence he had formed an acquaintance with Perseus, though he was far away; and when a letter roused in him the hope of a more intimate friendship and of great prosperity as a result, he went to visit the king and in a short time began to be regarded as his confidant and to be drawn into his secret conferences to a greater degree than he desired. [5] For by the promise of great rewards the king began to ask of him, since all the Roman generals and ambassadors were accustomed to avail themselves of his hospitality, that he should undertake to poison those about whom Perseus should communicate with him by letter. [6] The king said that he was aware that to prepare poison involved a great deal of trouble and risk; that it was prepared with too many persons sharing in the secret; moreover, that its administration was uncertain, whether doses were sufficiently powerful to accomplish the purpose or sufficiently safe to keep the act concealed. [7] He promised that he would supply a poison which could not be detected by any symptom, either while being given or after it was given. [8] Rammius, fearing that if he refused he himself would be the first to be a test of the poison, promised that he would do as the king [p. 343]wished and departed; nor did he wish to return³ to Brundisium until he had met Gaius Valerius, who was said to be in the neighbourhood of Chalcis. [9] Having first given him this information, by the order of Valerius he came with him to Rome. Being introduced into the senate, he reported what had occurred.