You must know, my loved one, that there are beings in the elements which almost appear like mortals, and which rarely allow themselves to become visible to yourrace. Wonderful salamanders glitter and sport in the flames; lean and malicious gnomes dwell deep within the earth; spirits, belonging to the air, wander through the forests; and a vast family of water spirits live in the lakes and streams and brooks. In resounding domes of crystal, through which the sky looks in with its sun and stars, these latter spirits find their beautiful abode; lofty trees of coral with blue and crimson fruits gleam in their gardens; they wander over the pure sand of the sea, and among lovely variegated shells, and amid all exquisite treasures of the old world, which the present is no longer worthy to enjoy; all these the floods have covered with their secret veils of silver, and the noble monuments sparkle below, stately and solemn, and bedewed by the loving waters which allure from them many a beautiful moss-flower and entwining cluster of sea grass. Those, however, who dwell there, are very fair and lovely to behold, and for the most part, are more beautiful than human beings. Many a fisherman has been so fortunate as to surprise some tender mermaid, as she rose above the waters and sang. He would then tell afar of her beauty, and such wonderful beings have been given the name of Undines. You, however, are now actually beholding an Undine.
Friedrich de la Motte Fouqué, Undine