Plutarch, Galba
Bernadotte Perrin, Ed.

25. Here, as we are told, the soldiers who first welcomed him and saluted him as emperor were no more than twenty-three. Therefore, although he was not sunken in spirit to match the weakness and effeminacy of his body, but was bold and adventurous in presence of danger, he began to be afraid. [2] The soldiers who were there, however, would not suffer him to desist, but surrounding his litter with their swords drawn, ordered it to be taken up, while Otho urged the bearers to hasten, saying to himself many times that he was a lost man. For he was overheard by some of the bystanders, and they were astonished rather than disturbed, owing to the small number of those who had ventured upon the deed. But as he was thus borne through the forum, he was met by as many more soldiers, and others again kept joining the party by threes and fours. [3] Then all crowded around the litter, saluting Otho as emperor and brandishing their drawn swords. At the camp, Martialis, the military tribune in charge of the watch at the time, who was not privy to the plot, as they say, but was confounded by their unexpected appearance and terrified, permitted them to enter. And after Otho was inside the camp, no one opposed him. For those who were ignorant of what was going on, scattered about as they were by ones and twos, were designedly enveloped by those who knew and were privy to the plot, and so gave in their adherence, at first through fear, and then under persuasion.

[4] News of this was carried at once to Galba in the Palatium and the priest was still standing there with the entrails in his hands, so that even men who were altogether indifferent and sceptical about such matters were confounded and filled with wonder at the divine portent. And now a motley crowd came streaming out from the forum; Vinius and Laco and some of the freedmen stood at Galba's side brandishing their naked swords; Piso went out and held conference with the guards on duty in the court; [5] and Marius Celsus, a man of worth, was sent off to secure the allegiance of the Illyrian legion encamped in what was called the Vipsanian portico.