Tomorrow night, the eve of May Day, is Walpurgisnacht. One Walpurgisnacht, according to Goethe's Faust, Mephistopheles and the eponymous anti-hero find themselves upon a lonely mountainside. "Do you not long for a broomstick?" asks Mephistopheles. "By this road we are still far from our destination."
Faust, however, is more preoccupied by the miserable weather. "How the storm blast is raging through the air!" he complains: "With what thumps it strikes against my neck." And Mephistopheles agrees: "You must lay hold of those old ribs of rock, or it will hurl you into the abyss. A mist thickens the night."
The next development takes them somewhat unawares, but it explains the enigmatic reference to broomsticks. A coven of witches suddenly appears from nowhere, for it turns out that the mountain is the Brocken, the highest peak of the Harz Mountains in Germany, on top of which witches are said to congregate to celebrate a Sabbath on Walpurgisnacht.
The legend is nicely explained in The Antiquary, a journal popular in Goethe's time. "The mountains of the Harz Forest in Germany, especially the Brocken, are scenes for tales of witches, demons, and apparitions. The occupation of the inhabitants, who are either miners or foresters, is of a kind that renders them peculiarly prone to superstition, and the natural phenomena they witness in pursuit of their solitary or subterranean professions are often set down by them to the interference of goblins or the power of magic."
The author then describes the Brocken spectre, a phenomenon well known to meteorologists: "Among the various legends current in that wild country, is one which supposes the Harz to be haunted with a kind of tutelar demon, in the shape of a wild man, of huge stature, his head wreathed with oak leaves, and his middle cinctured with the same. Many profess to have seen such a form traversing, with huge strides, in a line parallel to their own course, the opposite ridge of a mountain, when divided from it by a narrow glen."
And he goes on to give the explanation: "This optical deception, however, admits of a very simple explanation. When the rising sun [and according to analogy, the case will be the same at the setting] throws his rays over the Brocken upon the body of a man standing opposite to fine light clouds floating around or hovering past him, he need only fix his eye steadily upon them, and in all probability he will see the singular spectacle of his own shadow extending to the length of five or six hundred feet, at the distance of about two miles before him."