On the Garamantes (Herodotus)
Further inland to the southward, in the part of Libya where wild beasts are found, live the Garamantes, who avoid all intercourse with men, possess no weapons of war, and do not know how to defend themselves. Along the coast to the westward the neighbours of the Nasamones are the Macae. These people wear their hair in the form of a crest, shaving it close on either side of the head and letting it grow long in the middle; in war they carry ostrich skins for shields. The river Cinyps, which rises on a hill called the Hill of the Graces, runs through their territory to the sea. The Hill of the Graces is about twenty-five miles inland, and is densely wooded, unlike the rest of Libya so far described, which is bare of trees.
…Ten days' journey west of the Ammonians, along the belt of sand, there is another similar salt-hill and spring. This place, called Augila, is also inhabited and it is here that the Nasamonians come for their date harvest. Again at the same distance to the west is a salt-hill and spring, just as before, with date palms of the fruit-bearing kind, as in the other oases; and here live the Garamantes, a very numerous tribe of people, who spread soil over the salt to sow their seed in. From these people is the shortest route—thirty days' journey—to the Lotophagi; and it is amongst them that the cattle are found which walk backwards as they graze. The reason for this curious habit is provided by the formation of their horns, which bend forwards and downwards; this prevents them from moving forwards in the ordinary way, for, if they tried to do so, their horns would stick in the ground. In other respects they are just like ordinary cattle—except for the thickness and toughness of their hide. The Garamantes hunt the Ethiopian hole-men, or troglodytes, in four-horse chariots, for these troglodytes are exceedingly swift of foot—more so than any people of whom we have any information. They eat snakes and lizards and other reptiles and speak a language like no other, but squeak like bats.

Pliny's account of the army led by Balbus in the Fezzan against the Garamantes

…Beyond the Lesser Syrtis is the region of Phazania; the nation of Phazanii belonging to which, as well as the cities of Alele and Cilliba, we have subdued by force of arms, as also Cydamus, which lies over against Sabrata. After passing these places a range of mountains extends in a prolonged chain from east to west; these have received from our people the name of Black Mountains, either from the appearance which they naturally bear of having been exposed to the action of fire, or else because they have been scorched by the sun's rays. Beyond it lies the desert, and then Talgae, a city of the Garamantes, and Debris, … Garama, too, that most famous capital of the Garamantes, all of which places have been subdued by the Roman arms. It was on this occasion that Cornelius Balbus was honoured with a triumph. … Besides Cydamus and Garama, there were carried in procession the names and models of all the other nations and cities in the following order; Tabudium, a town ; Niteris, a tribe ; the town of Nigligemela, the tribe or town of Bubeium, the tribe Enipi, the town Thuben, the mountain known as the Black Mountain, Nitibrum, the towns called Rapsa, the tribe Discera, the town Debris, the river Nathabur, the town Thapsagum, the tribe Nannagi, the town Boin, the town Pege, the river Dasibari; and then the towns in the following order, of Baracum, Buluba, Alasit, Galia, Balla, Maxalla, Zigama, and Mount Gyri, which was preceded by an inscription stating that this was the place where precious stones were produced.

…Up to the present, it has been found impracticable to keep open the road that leads to the country of the Garamantes, as the robber bands of that people have filled up the wells with sand, which wells do not require to be digged to any great depth, if you but have knowledge of the locality.