The Deathbed of Louis XIV.

References for other Cases of Crystal Visions.
From dreams, in sleep or swoon, of a character difficult to believe in we pass by way of "hallucinations" to ghosts.

Everybody is ready to admit that dreams do really occur, because almost everybody has dreamed.

But everybody is not so ready to admit that sane and sensible men and women can have hallucinations, just because everybody has not been hallucinated.
On this point Mr.Francis Galton, in his Inquiries into Human Faculty (1833), is very instructive.

Mr.Galton drew up a short catechism, asking people how clearly or how dimly they saw things "in their mind's eye".
"Think of your breakfast-table," he said; "is your mental picture of it as clearly illuminated and as complete as your actual view of the scene ?" Mr.Galton began by questioning friends in the scientific world, F.R.S.'s and other savants.