I have always read that the ancient people believed in a barge transporting the sun. This would make sense to the ancient people that were near water to believe in this myth. The Ancient Egyptians are the only images I can find (thus far) of ancient people and the sun barge. It also looks as thought he moon is just under the sun. Two baboons are the escorts for the sun.
What else is known about the sun barges? A barge procession would take place for the dead. The barge of the dead would also be preserved for the afterlife. Many barges have been found in the tombs.