Fludd's dark universe. Engraving of a black square representing the dark universe, with the Latin words Et sic in infinitum (And so into infinity) along its edges. This artwork is from Utriusque cosmi, maioris scilicet et minoris, metaphysica, physica, atque technica historia (The metaphysical, physical, and technical history of the two worlds, namely the greater and the lesser), written by English physician, astrologer, and mystic Robert Fludd (1574-1637) in 1617.