in Thoreau’s Journal:

I do not know of any more exhilarating walking than up or down a broad field of smooth ice like this in a cold, glittering, winter day, when your rubbers give you a firm hold on the ice….

In the cold, clear, rough air from the northwest we walk amid what simple surroundings! Surrounded by our thoughts or imaginary objects, living in our ideas, not one in a million even sees the objects which are actually around him.