There are many curious and miraculously unusual happenings and things in nature, of which no human understands how they occur or how they relate to other things, but they exist nonetheless. And when people hear stories about them, they are amazed and terrified, but they cannot comprehend them. Thus it is with the Raven Stone, which many people talk about, but no one knows anything about with certainty. But it is known for sure that Raven Stones exist.
You have heard about Thieves’ Lights. They are similar to the Raven Stone and other invisible thieves’ lanterns. It is gruesome to relate how Thieves’ Lights are obtained. They are the fingers of unborn, innocent little children. For these purposes the fingers of already born and baptized children cannot be used.
And what sort of unborn little children are they? And how does one obtain the lights? When a female thief or murderer hangs or drowns herself, or is hanged or beheaded, and she is carrying a child inside her body, then you must go forth at midnight on the devil’s roads, not on God’s roads, with incantations and magic, not with prayer and blessings, and you must take an axe or a knife that has been used by an executioner, and with it you must open up the poor sinner’s belly, take out the child, cut off its fingers, and take them with you.
But this absolutely must all be done at midnight in the most perfect solitude and silence. Not even the softest sound, no “oh” and no sigh can escape the lips of the seeker. In this manner you obtain the lights, which you can burn whenever you want to. And however short they are, they will never burn up, but will always remain the same length.
These magic lights have the unusual nature and property that they ignite whenever and wherever their thievish owner wants them to. And they extinguish themselves as fast as his wish and thought.
With their help he can see everything, even in the densest and darkest night, whenever and wherever he wants. But they shine only for him and for no one else. He himself remains invisible, even though they illuminate everything else. Further, the horror within them gives them a mysterious power over sleep. In any room where they are lit a sleeper will snore so soundly that one could set off ten thunderbolts over his head without waking him. Just think how easy it is to steal things and carry them off under these conditions!
This story was translated by Professor D.L. Ashliman, and posted on his Folklinks site: http://www.pitt.edu/~dash/folktexts.html
He adds: “In later editions, Arndt’s editors softened this account by omitting the requirement that the dead person’s fingers used for thieves lights must be from an unborn child, stating only that they come from an unbaptized child. See, for example, “Der Rabenstein,” Mährchen und Jugenderinnerungen vol. 2, 3rd edition (Leipzig: Kommissions-Verlag von Karl Fr. Pfau, 1902), pp. 335-36.
The Raven Stones mentioned at the beginning of the above piece have similar qualities to the Thieves’ Lights. They too emit a light visible only to their owners, but their origin is not quite as horrible as that of the Thieves’ Lights. Raven Stones are undigested remains of the eyes of executed criminals. Arndt, in the chapter cited above, gives substantial detail about how these stones can be obtained from the ravens that picked out the eyes of the criminals on the gallows”
Source: Ernst Moritz Arndt, “Der Rabenstein,” Mährchen und Jugenderinnerungen vol. 2 (Berlin: G. Reimer, 1843), pp. 348-49. To read the original German: http://books.google.com/books?id=lGg6AAAAcAAJ&pg=PA348#v=onepage&q&f=false