When the artist Larry Harvey first set fire to a 9-foot wooden effigy of a man and began a ceremony now celebrated annually at Black Rock City, Nevada, he had never heard of the famous 1973 cult horror film, “The Wicker Man,” which took its cue from an alleged Celtic practice of human sacrifice. In fact, actual record of this type of human sacrifice is extremely sketchy. Two Ancient Roman writers, both biased and taking information from a now lost source, have on record that Ancient Celtic British peoples would ritually burn sacrificial victims trapped in a wooden sculpture to propitiate the gods. Julius Caesar writes in the first century BCE: “figures of vast size, the limbs of which formed of osiers (type of willow tree) they fill with living men,” and set ablaze. According to the website “Balkan Celts”, a very scant piece of archaeological evidence attesting to the existence of this type of human sacrifice among the Celts comes from 1st-c BCE Thracian Celtic coins showing a giant figure with a burning head, perhaps reflecting a thunder deity called Taranis.
Source(s): Https://balkancelts.wordpress.com/2013/10/05/the-wicker-man/ .