Zurbarán - Saint Francis in Meditation (1635-1639), Still Life (1660s)
There is no darker and more confounding image of the self lost in spiritual ecstasy than Zurbarán's painting of Saint Francis with his face shadowed beneath his cowl. The painting is a disturbing masterpiece of light and dark: look long enough and you can clearly see his features, but at first glance or from a distance there appears to be nothing there but blackness.
Courbet and other French modern artists were ravished by this painting when it was in Paris, before the National Gallery bought it in 1853. Zurbarán dedicated a gift comparable with Caravaggio's to praising the ascetic religious life. He even does this in his still life scenes, with their monastic plainness.