What archeological findings are cited as evidence of viking berserkers? Are there texts from the viking age, or is it exclusively accounts from centuries later?

While more can always be said, I discussed very few contemporary literary evidence (10th century poetry, but only extant in form of the citation in medieval manuscripts) as well as possibly relevant artifacts before in the following posts:

Were Berserkers really as crazy as the historical records show?
In The Northman, there are multiple scenes where Vikings seemed to feel possessed by the spirit of a wolf. Did these Vikings literally believe they had become wolves, or did they just feel akin to certain archetypal characteristics of wolves (eg pack loyalty, viciousness, fearlessness, etc.)?