This is a fairytale that Jung recounts in Archetypes and the Collective Unconscious in the essay, "The Phenomenology of the Spirit in Fairytales" [p. 231-233]. I haven't found a "storyteller-like" telling of the tale online, so I will reproduce Jung's re-telling here (unembellished though it may be).
I was reminded of this story by Sealchan's talk about dreams of trees and what they might represent. Also, a while back I brought up this story in an e-mail to Remo Roth as an illustration of the only way I feel comfortable approaching the concept of the Subtle Body (which I equate here with the horse symbols).
However we see it, it's a rich story that reflects a good chunk of the individuation process.
Enjoy!
-Matt
The Princess in the Tree
(collected by Grimm)
While the young man is watching his pigs in the wood, he discovers a large tree, whose branches lose themselves in the clouds. "How would it be," says he to himself, "if you were to look at the world from the top of that great tree?" So he climbs up, all day long he climbs, without even reaching the branches. Evening comes, and he has to pass the night in a fork of the tree. Next day he goes on climbing and by noon has reached the foliage. Only towards evening does he come to a village nestling in the branches. The peasants who live there give him food and shelter for the night. In the morning he climbs still further. Towards noon, he reaches a castle in which a young girl lives. Here he finds that the tree goes no higher. She is a king's daughter, held prisoner by a wicked magician. So the young man stays with the princess, and she allows him to go into all the rooms of the castle: one room alone she forbids him to enter. But curiosity is too strong. He unlocks the door, and there in the room he finds a raven fixed to the wall with three nails. One nail goes through his throat, the two others through the wings. The raven complains of thirst and the young man, moved by pity, gives him water to drink. At each sip a nail falls out, and at the third sip the raven is free and flies out at the window. When the princess hears of it she is very frightened and says, "That was the devil who enchanted me! It won't be long now before he fetches me again." And one fine morning she has indeed vanished.
The young man now sets out in search of her and, as we have described above, meets the wolf. In the same way he meets a bear and a lion, who also give him some hairs. In addition the lion informs him that the princess is imprisoned nearby in a hunting-lodge. The young man finds the house and the princess, but is told that flight is impossible, because the hunter possesses a three-legged white horse that knows everything and would infallibly warn its master. Despite that, the young man tries to flee away with her, but in vain. The hunter overtakes him but, because he had saved his life as a raven, lets him go and rides off again with the princess. When the hunter has disappeared into the wood, the young man creeps back to the house and persuades the princess to wheedle from the hunter the secret of how he obtained his clever white horse. This she successfully does in the night, and the young man, who has hidden himself under the bed, learns that about an hour's journey from the hunting-lodge there dwells a witch who breeds magic horses. Whoever was able to guard the foals for three days might choose a horse as a reward. In former times, said the hunter, she used to make a gift of twelve lambs into the bargain, in order to satisfy the hunger of the twelve wolves who lived in the woods near the farmstead, and prevent them from attacking; but to him she gave no lambs. So the wolves followed him as he rode away, and while crossing the borders of her domain they succeeded in tearing off one of his horse's hoofs. That was why it had only three legs.
Then the young man made haste to seek out the witch and agreed to serve her on condition that she gave him not only a horse of his own choosing but twelve lambs as well. To this she consented. Instantly she commanded the foals to run away, and, to make him sleepy, she gave him brandy. He drinks, falls asleep, and the foals escape. On the first day he catches them with the help of the wolf, on the second day the bear helps him, and on the third the lion. He can now go and choose his reward. The witch's little daughter tells him which horse her mother rides.
This is naturally the best horse, and it too is white. Hardly has he got it out of the stall when the witch pierces the four hoofs and sucks the marrow out of the bones. From this she bakes a cake and gives it to the young man for his journey. The horse grows deathly weak, but the young man feeds it on the cake, whereupon the horse recovers its former strength. He gets out of the woods unscathed after quieting the twelve wolves with the twelve lambs. He then fetches the princess and rides away with her. But the three-legged horse calls out to the hunter, who sets off in pursuit and quickly catches up with them, because the four-legged horse refuses to gallop. As the hunter approaches, the four-legged horse cries out to the three-legged, "Sister, throw him off!" The magician is thrown and trampled to pieces by the two horses. The young man sets the princess on the three-legged horse, and the pair of them ride away to her father's kingdom, where they get married. The four-legged horse begs him to cut off both their heads, for otherwise they would bring disaster upon him. This he does, and the horses are transformed into a handsome prince and a wonderfully beautiful princess, who after a while repair "to their own kingdom." They had been changed into horses by the hunter, long ago.