Julius Caesar's War Commentaries
De Bello Gallico (Gallic Wars): Book 4
[4.23]
These matters being arranged, finding the weather favorable for his voyage, he set sail about the third watch, and ordered the horse to march forward to the further port, and there embark and follow him. As this was performed rather tardily by them, he himself reached Britain with the first squadron of ships, about the fourth hour of the day, and there saw the forces of the enemy drawn up in arms on all the hills.
The nature of the place was this: the sea was confined by mountains so close to it that a dart could be thrown from their summit upon the shore. Considering this by no means a fit place for disembarking, he remained at anchor till the ninth hour, for the other ships to arrive there. Having in the mean time assembled the lieutenants and military tribunes, he told them both what he had learned from Volusenus, and what he wished to be done; and enjoined them (as the principle of military matters, and especially as maritime affairs, which have a precipitate and uncertain action, required) that all things should be performed by them at a nod and at the instant.
Having dismissed them, meeting both with wind and tide favorable at the same time, the signal being given and the anchor weighed, he advanced about seven miles from that place, and stationed his fleet over against an open and level shore.
Thank you. Original sources are SO exciting!