( Story told by Swami Vivekananda )
There was once a minister to a great king. He fell into disgrace. The king, as a punishment, ordered him to be shut up in the top of a very high tower. This was done, and the minister was left there to perish. He had a faithful wife, however, who came to the tower at night and called to her husband at the top to know what she could do to help him. He told her to return to the tower the following night and bring with her a long rope, some stout twine, pack thread, silken thread, a beetle, and a little honey.
Wondering much, the good wife obeyed her husband, and brought him the desired articles. The husband directed her to attach the silken thread firmly to the beetle, then to smear its horns with a drop of honey, and to set it free on the wall of the tower, with its head pointing upwards. She obeyed all these instructions, and the beetle started on its long journey. Smelling the honey ahead it slowly crept onwards, in the hope of reaching the honey, until at last it reached the top of the tower, when the minister grasped the beetle, and got possession of the silken thread. He told his wife to tie the other end to the pack thread, and after he had drawn up the pack thread, he repeated the process with the stout twine, and lastly with the rope.
Then the rest was easy. The minister descended from the tower by means of the rope, and made his escape. In this body of ours the breath motion is the ‘silken thread’; by laying hold of and learning to control it we grasp the pack thread of the nerve currents, and from these the stout twine of our thoughts, and lastly the rope of Prana, controlling which we reach freedom.
Source : The Complete Works of Swami Vivekananda/Volume 1/Lectures And Discourses/Breathing