What is called poetic insight is the gift of discerning, in this sphere of strangely-mingled elements, the beauty and the majesty which are compelled… - Nathaniel Hawthorne

What other dungeon is so dark as one's own heart! What jailer so inexorable as one's self!

The marble was all burnt into perfect, snow-white lime. But on its surface, in the midst of the circle,—snow-white too, and thoroughly converted into lime,—lay a human skeleton, in the attitude of a person who, after long toil, lies down to long repose. Within the ribs—strange to say—was the shape of a human heart.
"Was the fellow's heart made of marble?" cried Bertram...
"At any rate, it is burnt into what looks like a special good lime... my kiln is half a bushel the richer for him." ...
[T]he rude lime-burner lifted his pole, and, letting it fall upon the skeleton, the relics of Ethan Brand were crumbled into fragments.

... for when a man's spirit has been thoroughly crushed, he may be peevish at small offenses, but never resentful of great ones.