Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[182] Now Solomon had a divine sagacity in all things, and was very diligent and studious to have things done after an elegant manner; so he did not neglect the care of the ways, but he laid a causeway of black stone along the roads that led to Jerusalem, which was the royal city, both to render them easy for travelers, and to manifest the grandeur of his riches and government. He also parted his chariots, and set them in a regular order, that a certain number of them should be in every city, still keeping a few about him; and those cities he called the cities of his chariots. And the king made silver as plentiful in Jerusalem as stones in the street; and so multiplied cedar trees in the plains of Judea, which did not grow there before, that they were like the multitude of common sycamore trees. He also ordained the Egyptian merchants that brought him their merchandise to sell him a chariot, with a pair of horses, for six hundred drachmae of silver, and he sent them to the kings of Syria, and to those kings that were beyond Euphrates.