In Dante’s Purgatorio, souls are surprised to see that their visitor casts a shadow and thus is not dead:

When they perceiv’d that through my body I
Gave way not for the rays to pass, their song
Straight to a long and hoarse exclaim they chang’d;
And two of them, in guise of messengers,
Ran on to meet us, and inquiring ask’d:
“Of your condition we would gladly learn.”

That’s a bit of a puzzle, note Roberto Casati and Patrick Cavanagh. “To be visible, supernatural entities must reflect light (if they do not emit it). But as a consequence they must be opaque to at least some light, and thus they should cast shadows.”

(Roberto Casati and Patrick Cavanagh, The Visual World of Shadows, 2019. Related: Why do ghosts wear clothes?)