The Carthaginian navigator Hanno circumnavigated Africa circa 500 BC. Hanno observed that, at the southern end of the continent, the noonday sun was shining in the north. This, according to Herodotus, was clearly absurd. In fact, Hanno's claim proves that he did indeed circumnavigate Africa; he would not likely have imagined the sun shining in the "wrong" part of the sky had he not seen it for himself.
[Hanno went as far as Sierra Leone in his explorations. In the Greek translation of his report he tells of seeing "gorillai," the name of which he allegedly learned from local informants -- and which he thought were members of a tribe of hairy women!]