Salvator Mundi
Iconographically, the crystal sphere relates to the heavens. In Ptolemaic cosmology, the stars were embedded in a fixed celestial crystalline sphere (composed of aether), with the spherical Earth at the center of the universe. "So what you've got in the "Salvator Mundi"", Kemp states, "is really 'a savior of the cosmos', and this is a very Leonardesque transformation."