According to the Puranic-Tantric picture of the world, our earth is at the centre of a vast multidimensional and multilayered universe, which is known as the “brahmic egg.” Tradition speaks of countless such universe-islands floating in the infinite cosmic ocean. The observable material earth is merely the coarsest and least spectacular aspect of the universe. The universe reveals its true nature only to trained meditative vision. As the Puranas and Tantras describe it, the earth is really part of a vast circular plane called bhu-mandala (earth round), with a diameter of 500 million yojanas (4 billion miles). This corresponds with the size of our solar system if we consider Pluto’s mean distance from the sun, which is approx. 3.6 billion miles.
Tantra: The Path of Ecstasy p.26