This chart shows three ancient structures of the universe and three sixteenth-century ones. Note that the main difference in the ancient cosmographies is the ordering of the inferior planets in the case of the Platonic and Ptolemaic systems. The Egyptian system, depicting a heliocentric Mercury and Venus, is a rare representation and of suspect provenance. The semi-Tychonic system better accounted for the orbit of Mars. The Tychonic and Copernican systems are mathematically equivalent.