The first philosophical cosmologists reacted against, or sometimes built upon, popular mythical conceptions that had existed in the Greek world for some time. Some of these popular conceptions can be gleaned from the poetry of Homer and Hesiod. In Homer, the Earth was viewed as a flat disk afloat on the river of Oceanus and overlooked by a hemispherical sky with sun, moon, and stars. The Sun (Helios) traversed the heavens as a charioteer and sailed around the Earth in a golden bowl at night. Sun, earth, heaven, rivers, and winds could be addressed in prayers and called to witness oaths. Natural fissures were popularly regarded as entrances to the subterranean house of Hades and his predecessors, home of the dead.[28]:45 Influences from other cultures always afforded new themes.