Tacitus, Annals 2.69
On the way from Egypt, Germanicus learned that all orders issued by him to the legions or the cities had been rescinded or reversed. Hence galling references to Piso: nor were the retorts directed by him against the prince less bitter. Then Piso determined to leave Syria. Checked almost immediately by the ill-health of Germanicus, then hearing that he had rallied and that the vows made for his recovery were already being paid, he took his lictors and swept the streets clear of the victims at the altars, the apparatus of sacrifice, and the festive populace of Antioch. After this, he left for Seleucia, awaiting the outcome of the malady which had again attacked Germanicus. The cruel virulence of the disease was intensified by the patient's belief that Piso had given him poison; and it is a fact that explorations in the floor and walls brought to light the remains of human bodies, spells, curses, leaden tablets engraved with the name Germanicus, charred and blood-smeared ashes,68 and others of the implements of witchcraft by which it is believed the living soul can be devoted to the powers of the grave. At the same time, emissaries from Piso were accused of keeping a too inquisitive watch upon the ravages of the disease.