Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

69. The assembly passed all these measures without a dissentient voice, and was then dissolved.¹ And now the Four Hundred were introduced into the council-chamber. The manner was as follows:—The whole population were always on service, either manning the walls or drawn up at their places of arms, for the enemy were at Decelea². [2] On the day of the assembly those who were not in the conspiracy were allowed to go home as usual, while the conspirators were quietly told to remain, not actually by their arms, but at a short distance; if anybody opposed what was doing they were to arm and interfere. [3] There were also on the spot some Andrians and Tenians, three hundred Carystians, and some of the Athenian colonists from Aegina³, who received similar instructions; they had all been told to bring with them from their homes their own arms for this especial purpose⁴. [4] Having disposed their forces the Four Hundred arrived, every one with a dagger concealed about his person, and with them a bodyguard of a hundred and twenty Hellenic youths whose services they used for any act of violence which they had in hand. They broke in upon the council of five hundred as they sat in the councilchamber, and told them to take their pay and begone. They had brought with them the pay of the senators for the remainder of their yearly term of office, which they handed to them as they went out.