Louis XVII's short life was the stuff of nightmares. He lost his parents to the guillotine.

He was locked in Paris' Temple prison for three years -- for part of that time, in solitary confinement in a darkened cell, without anyone to wash him or clean up after him, said historian Philippe Delorme.

The boy finally died of tuberculosis in 1795, his body reportedly ravaged by tumors and scabies.

The child's corpse was dumped in a common grave -- but first, a doctor secretly carved out his heart in keeping with a tradition of preserving royal hearts separate from their bodies.