Around 360 BC, in his Timaeus, Plato used 4 of the regular solids to serve as atoms of the 4 elements. He wrote:

To the earth then, which is the most stable of bodies and the most easily modelled of them, may be assigned the form of a cube, and the remaining forms to the other elements—to fire the tetrahedron, to air the octahedron, and to water the icosahedron—according to their degrees of lightness or heaviness or power, or want of power, of penetration.