Who was Erich von Däniken? Controversial author behind ancient alien ideas dies at 90

In the book, the author claimed that the Mayan and Egyptian civilisations were visited by extraterrestrial beings, who then instructed them on technology way ahead of the times, which helped these socities make astounding structures like the pyramids.

After 'Chariots of the Gods?' came more than 24 books on similar themes, which made Von Däniken into a literary niche unto himself, where he mixed fact and fantasy, going against scientific evidence.

As per Swiss public broadcaster SRF, Von Däniken's books sold around 70 million copies in more than 30 languages, which makes him one of the most widely read authors of the country.

Von Däniken worked as a waiter as well as a barkeeper after he left school in 1954.

In 1964, he was appointed manager of a hotel in the exclusive resort town of Davos and began writing his first book. Its publication and rapid commercial success were quickly followed by accusations of tax dodging and financial impropriety, for which he again spent time behind bars.

But as his book took off, he emerged from prison as a best-selling author.

Still, he never presented the smoking gun to fulfil astronomer Carl Sagan's famous adage that "extraordinary claims require extraordinary evidence".

"He ... says that the astonishing astronomical information ancient civilizations, such as the Mayan, had is proof that there were some space travelers around to teach it to them. This fits in with his general questioning of the ability of the Egyptians to build the pyramids, or the Easter Islanders to erect those massive stone heads," the New York Times wrote in 1974.

"His method is to use a negative - ancient peoples couldn't have done or thought all the things they did - to prove a positive - that the ancient people were the beneficiaries of some kind of cosmological Point 4 (development assistance) programme."

Such criticism never knocked von Daeniken off his stride.

"We owe it to our self-respect to be rational and objective," he wrote. "At some time or other every daring theory seemed to be a Utopia. How many Utopias have long since become everyday realities!"

In a treatise on his website, von Daeniken said he was not an esoteric, and that his work served to debunk "a world of religious and unfortunately often scientific humbugs".

"From countless old written records I know that these 'gods' promised to return. Then we will experience the god shock, a total catastrophe in religion and science. And everything would have been so easy to understand - without this god shock. The evidence speaks a clear language. That is what drives me."

With AP, Reuters inputs