in Thoreau’s Journal:

The first really foggy morning yet before I rise I hear the song of birds from out it—like the bursting of its bubbles with music—the bead on liquids just uncorked. Their song gilds thus the frostwork of the morning— As if the fog were a great sweet froth on the surface of land and water—whose fixed air escaped—whose bubbles burst with music. The sound of its evaporation—the fixed air of the morning just brought from the cellars of the night escaping.— The morning twittering of birds in perfect harmony with it. I came near awaking this morning. I am older than last year   the mornings are further between— The days are fewer— Any excess—to have drunk too much water even, the day before is fatal to the morning’s clarity—but in health the sound of a cow bell is celestial music. O might I always wake to thought & poetry—regenerated! Can it be called a morning—if our senses are not clarified so that we perceive more clearly—if we do not rise with elastic vigor? How wholesome these fogs which some fear—they are cool medicated vapor baths—mingled by nature which bring to our senses all the medical properties of the meadows. The touchstones of health— Sleep with all your windows open and let the mist embrace you.