The Annals and the Histories · Ann. 12.47

Rhadamistus at first threw himself into his embraces, feigning respect and calling him father-in-law and parent. He swore an oath too that he would do him no violence either by the sword or by poison. At the same time he drew him into a neighbouring grove, where he assured him that the appointed sacrifice was prepared for the confirmation of peace in the presence of the gods. It is a custom of these princes, whenever they join alliance, to unite their right hands and bind together the thumbs in a tight knot; then, when the blood has flowed into the extremities, they let it escape by a slight puncture and suck it in turn. Such a treaty is thought to have a mysterious sanctity, as being sealed with the blood of both parties. On this occasion he who was applying the knot pretended that it had fallen off, and suddenly seizing the knees of Mithridates flung him to the ground. At the same…

Cornelius Tacitus · trans. Church & Brodribb, 1876
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