C. Julius Caesar, Gallic War

During the short part of summer which remained, Caesar, although in these countries, as all Gaul lies toward the north, the winters are early, nevertheless resolved to proceed into Britain, because he discovered that in almost all the wars with the Gauls succors had been furnished to our enemy from that country; and even if the time of year should be insufficient for carrying on the war, yet he thought it would be of great service to him if he only entered the island, and saw into the character of the people, and got knowledge of their localities, harbors, and landing-places, all which were for the most part unknown to the Gauls. For neither does any one except merchants generally go thither, nor even to them was any portion of it known, except the sea-coast and those parts which are opposite to Gaul. Therefore, after having called up to him the merchants from all parts, he could learn neither what was the size of the island, nor what or how numerous were the nations which inhabited it, nor what system of war they followed, nor what customs they used, nor what harbors were convenient for a great number of large ships.