The 5 platonic solids are considered cosmic solids due to their connection to nature that was discovered by Plato. The cube represents the earth, the octahedron represents the air, the tetrahedron represents the fire, the icosahedron represents the water, and the dodecahedron represents the universe.
First mentioned by Plato in his 'Timaeus', written in 360 BC. In the Timaeus Plato presents an elaborately account of the formation of the universe and an explanation of its impressive order.