Besides negotiating by means of conferences, the Parthian monarchs often sent out to neighboring states, and in return received from them formal embassies. The ambassadors in every case conveyed, as a matter of course, gifts to the prince to whom they were accredited, which might consist of articles of value, or of persons. Augustus included an Italian slave-girl among the presents which he transmitted to Phraates IV.; and Artabanus III. sent a Jewish giant to Tiberius. The object of an embassy was sometimes simply to congratulate; but more often the ambassadors were instructed to convey certain demands, or proposals, from their own prince to the head of the other nation, whereto his assent was required, or requested. These proposals were commonly formulated in a letter from the one prince to the other, which it was the chief duty of the ambassadors to convey safely. Free powers to conclude a treaty at their discretion were rarely, or never, entrusted to them. Their task was merely to deliver the royal letter, to explain its terms, if they were ambiguous, and to carry back to their own monarch the reply of the foreign sovereign. The sanctity of the ambassadorial character was invariably respected by the Parthians, who are never even taxed with a violation of it. As a security for the performance of engagements, or for the permanent maintenance of a friendly attitude, it was usual in the East during the Parthian period to require, and give, hostages. The princes who occupied the position of Parthian feudatories gave hostages to their suzerain, who were frequently their near relations, as sons or brothers. And a practice grew up of the Parthian monarchs themselves depositing their own sons or brothers with the Roman Emperor, at first perhaps merely for their own security, but afterwards as pledges for their good behavior. Such hostages lived at the expense of the Roman court, and were usually treated with distinction. In the event of a rupture between their country and Rome, they had little to fear. Rome found her advantage in employing them as rivals to a monarch with whom she had quarrelled, and did not think it necessary to punish them for his treachery or inconstancy.