in Thoreau’s Journal:

Nature provides shelter for her creatures in various ways. If the musquash, etc., has no longer extensive fields of weed and grass to crawl in, what an extensive range it has under the ice of the meadows and riversides! for, the water settling directly after freezing, an icy roof of indefinite extent is thus provided for it, and it passes almost its whole winter under shelter, out of the wind and invisible to men.