Titus Livius (Livy), The History of Rome, Book 44
Alfred C. Schlesinger, Ph.D., Ed.

23. While these events were occurring in Italy, Perseus decided that since he had discovered that the Romans had entered the pass and that the final crisis of the war impended, he must no longer postpone the project which he could not bring himself to complete because expenditure of money was required-namely, gaining the adherence of Gentius, king of Illyria. [2] Inasmuch as Perseus had agreed through his envoy Hippias¹ on a payment of three [p. 165]hundred talents of silver, on condition of an exchange² of hostages, he sent Pantauchus, one of his most trusty friends, to complete the agreement. [3] At Meteon in the region of Labeatis, Pantauchus met the Illyrian king; there he received the king's oath and his hostages. Gentius too sent an envoy named Olympio to require the oath and the hostages of Perseus.' [4] Others were sent with him to receive the money; and, at Pantauchus' suggestion, Parmenio and Morcus were named as envoys to go with the Macedonians to Rhodes. [5] To them instructions were given to set out for Rhodes only after the oath, the hostages, and the money had been received; it was thought that by the prestige of two kings at once the Rhodians could be induced to war with the Romans, and that once the kings were joined by the state to which [6??] belonged a unique reputation for sea-power, no hope on land or sea would be left the Romans.

[7] On the arrival of the Illyrians, Perseus left his camp at the Elpeüs River with all his cavalry and met them at Dium. [8] There the terms agreed upon were executed in the presence of the surrounding column of cavalry, whom the king wished to be present at the ratification of the alliance with Gentius, thinking that it would somewhat raise their spirits. [9] The hostages were also given and received in the sight of all, those who were to receive the money were sent to the royal treasury at Pella and those who were to accompany the Illyrian envoys to Rhodes were ordered to take ship at Thessalonica. [10] Metrodorus³ was at that port, a recent arrival from Rhodes, who stated, on the authority of Dinon and Polyaratus, the [p. 167]heads of the state,⁴ that the Rhodians were ready for⁵ war. Metrodorus was assigned as the leader of the combined embassy with the Illyrians.