Gallic Wars Book 6 (53 B.C.E.) - The burning man ritual
tr. by W.A. McDevitte and W.S. Bohn
...... The nation of all the Gauls is extremely devoted to superstitious rites; and on that account they who are troubled with unusually severe diseases, and they who are engaged in battles and dangers, either sacrifice men as victims, or vow that they will sacrifice them, and employ the Druids as the performers of those sacrifices; because they think that unless the life of a man be offered for the life of a man, the mind of the immortal gods can not be rendered propitious, and they have sacrifices of that kind ordained for national purposes. Others have figures of vast size, the limbs of which formed of osiers they fill with living men, which being set on fire, the men perish enveloped in the flames. They consider that the oblation of such as have been taken in theft, or in robbery, or any other offense, is more acceptable to the immortal gods; but when a supply of that class is wanting, they have recourse to the oblation of even the innocent.
They worship as their divinity, Mercury in particular, and have many images of him, and regard him as the inventor of all arts, they consider him the guide of their journeys and marches, and believe him to have great influence over the acquisition of gain and mercantile transactions. Next to him they worship Apollo, and Mars, and Jupiter, and Minerva; respecting these deities they have for the most part the same belief as other nations: that Apollo averts diseases, that Minerva imparts the invention of manufactures, that Jupiter possesses the sovereignty of the heavenly powers; that Mars presides over wars. To him, when they have determined to engage in battle, they commonly vow those things which they shall take in war. When they have conquered, they sacrifice whatever captured animals may have survived the conflict, and collect the other things into one place. In many states you may see piles of these things heaped up in their consecrated spots; nor does it often happen that any one, disregarding the sanctity of the case, dares either to secrete in his house things captured, or take away those deposited; and the most severe punishment, with torture, has been established for such a deed…..