in Thoreau’s Journal:

To the Beeches.  A misty afternoon, but warm, threatening rain. Standing on Walden, whose eastern shore is laid waste, men walking on the hillside a quarter of a mile off are singularly interesting objects, seen through the mist, which has the effect of a mirage. The persons of the walkers are black on the snowy ground, and the limited horizon makes them the more important in the scene. This kind of weather is very favorable to our landscape. I must not forget the lichen-painted boles of the beeches.