in Thoreau’s Journal:

The temperature of the air and the clearness or serenity of the sky are indispensable to a knowledge of a day, so entirely do we sympathize with the moods of nature. It is important to know of a day that is past whether it was warm or cold, clear or cloudy, calm or windy, etc.

They are very different seasons in the winter when the ice of the river and meadows and ponds is bare, — blue or green, a vast glittering crystal, —and when it is all covered with snow or slosh; and our moods correspond. The former may be called a crystalline winter.