Sources from the ancient world
Tacitus' Germania
According to Strabo (64/63 B.C.E. - 21 C.E.) in his Geography (4.1.13): "The Romans put a stop both to these customs and to the ones connected with sacrifice and divination, as they were in conflict with our own ways: for example, they would strike a man who had been consecrated for sacrifice in the back with a sword, and make prophecies based on his death-spasms; and they would not sacrifice without the presence of the Druids. Other kinds of human sacrifices have been reported as well: some men they would shoot dead with arrows and impale in the temples; or they would construct a huge figure of straw and wood, and having thrown cattle and all manner of wild animals and humans into it, they would make a burnt offering of the whole thing." - (trans. by Benjamin Fortson, in Koch and Carey 1995, 18).
According to Julius Caesar (writing c. 15 March, 44 B. C. E.) De Bello Gallico 6.16):
"All the people of Gaul are completely devoted to religion, and for this reason those who are greatly affected by diseases and in the dangers of battle either sacrifice human victims or vow to do so using the Druids as administrators to these sacrifices, since it is judged that unless for a man's life a man's life is given back, the will of the immortal gods cannot be placated. In public affairs they have instituted the same kind of sacrifice. Others have effigies of great size interwoven with twigs, the limbs of which are filled up with living people which are set on fire from below, and the people are deprived of life surrounded by flames. It is judged that the punishment of those who participated in theft or brigandage or other crimes are more pleasing to the immortal gods; but when the supplies of this kind fail, they even go so low as to inflict punishment on the innocent." - (trans. Anne Lea, in Koch and Carey 1995. 22).
According to Tacitus in his book of Germania - chapter 12 Punishments:
"Administration of Justice. In their councils an accusation may be preferred or a capital crime prosecuted. Penalties are distinguished according to the offense. Traitors and deserters are hanged on trees; the coward, the unwarlike, the man stained with abominable vices, is plunged into the mire of the morass with a hurdle put over him. This distinction in punishment means that crime, they think, ought, in being punished, to be exposed, while infamy ought to be buried out of sight- Lighter offenses, too, have penalties proportioned to them; he who is convicted, is fined in a certain number of horses or of cattle. Half of the fine is paid to the king or to the state, half to the person whose wrongs are avenged and to his relatives. In these same councils they also elect the chief magistrates, who administer law in the cantons and the towns. Each of these has a hundred associates chosen from the people, who support him with their advice and influence." - (http://www.unrv.com/tacitus/tacitus-germania-3.php)
According to Tacitus in his book of Germania - chapter 40 Langobards:
"What on the contrary ennobles the Langobards is the smallness of their number, for that they, who are surrounded with very many and very powerful nations, derive their security from no obsequiousness or plying; but from the dint of battle and adventurous deeds. There follow in order the Reudignians, and Aviones, and Angles, and Varinians, and Eudoses, and Suardones and Nuithones; all defended by rivers or forests. Nor in one of these nations does aught remarkable occur, only that they universally join in the worship of Herthum; that is to say, the Mother Earth. Her they believe to interpose in the affairs of man, and to visit countries. In an island of the ocean stands the wood Castum: in it is a chariot dedicated to the Goddess, covered over with a curtain, and permitted to be touched by none but the Priest. Whenever the Goddess enters this her holy vehicle, he perceives her; and with profound veneration attends the motion of the chariot, which is always drawn by yoked cows.
Then it is that days of rejoicing always ensue, and in all places whatsoever which she descends to honor with a visit and her company, feasts and recreation abound. They go not to war; they touch no arms; fast laid up is every hostile weapon; peace and repose are then only known, then only beloved, till to the temple the same priest reconducts the Goddess when well tired with the conversation of mortal beings. Anon the chariot is washed and purified in a secret lake, as also the curtains; nay, the Deity herself too, if you choose to believe it. In this office it is slaves who minister, and they are forthwith doomed to be swallowed up in the same lake. Hence all men are possessed with mysterious terror; as well as with a holy ignorance what that must be, which none see but such as are immediately to perish. Moreover this quarter of the Suevians stretches to the middle of Germany." - (http://www.unrv.com/tacitus/tacitus-germania-11.php)
According to Julius Caesar (writing c. 15 March, 44 B. C. E.) De Bello Gallico 6.16):
"All the people of Gaul are completely devoted to religion, and for this reason those who are greatly affected by diseases and in the dangers of battle either sacrifice human victims or vow to do so using the Druids as administrators to these sacrifices, since it is judged that unless for a man's life a man's life is given back, the will of the immortal gods cannot be placated. In public affairs they have instituted the same kind of sacrifice. Others have effigies of great size interwoven with twigs, the limbs of which are filled up with living people which are set on fire from below, and the people are deprived of life surrounded by flames. It is judged that the punishment of those who participated in theft or brigandage or other crimes are more pleasing to the immortal gods; but when the supplies of this kind fail, they even go so low as to inflict punishment on the innocent." - (trans. Anne Lea, in Koch and Carey 1995. 22).
According to Tacitus in his book of Germania - chapter 12 Punishments:
"Administration of Justice. In their councils an accusation may be preferred or a capital crime prosecuted. Penalties are distinguished according to the offense. Traitors and deserters are hanged on trees; the coward, the unwarlike, the man stained with abominable vices, is plunged into the mire of the morass with a hurdle put over him. This distinction in punishment means that crime, they think, ought, in being punished, to be exposed, while infamy ought to be buried out of sight- Lighter offenses, too, have penalties proportioned to them; he who is convicted, is fined in a certain number of horses or of cattle. Half of the fine is paid to the king or to the state, half to the person whose wrongs are avenged and to his relatives. In these same councils they also elect the chief magistrates, who administer law in the cantons and the towns. Each of these has a hundred associates chosen from the people, who support him with their advice and influence." - (http://www.unrv.com/tacitus/tacitus-germania-3.php)
According to Tacitus in his book of Germania - chapter 40 Langobards:
"What on the contrary ennobles the Langobards is the smallness of their number, for that they, who are surrounded with very many and very powerful nations, derive their security from no obsequiousness or plying; but from the dint of battle and adventurous deeds. There follow in order the Reudignians, and Aviones, and Angles, and Varinians, and Eudoses, and Suardones and Nuithones; all defended by rivers or forests. Nor in one of these nations does aught remarkable occur, only that they universally join in the worship of Herthum; that is to say, the Mother Earth. Her they believe to interpose in the affairs of man, and to visit countries. In an island of the ocean stands the wood Castum: in it is a chariot dedicated to the Goddess, covered over with a curtain, and permitted to be touched by none but the Priest. Whenever the Goddess enters this her holy vehicle, he perceives her; and with profound veneration attends the motion of the chariot, which is always drawn by yoked cows.
Then it is that days of rejoicing always ensue, and in all places whatsoever which she descends to honor with a visit and her company, feasts and recreation abound. They go not to war; they touch no arms; fast laid up is every hostile weapon; peace and repose are then only known, then only beloved, till to the temple the same priest reconducts the Goddess when well tired with the conversation of mortal beings. Anon the chariot is washed and purified in a secret lake, as also the curtains; nay, the Deity herself too, if you choose to believe it. In this office it is slaves who minister, and they are forthwith doomed to be swallowed up in the same lake. Hence all men are possessed with mysterious terror; as well as with a holy ignorance what that must be, which none see but such as are immediately to perish. Moreover this quarter of the Suevians stretches to the middle of Germany." - (http://www.unrv.com/tacitus/tacitus-germania-11.php)