in Thoreau’s Journal:

A fair day, but a cool wind still, from the snow-covered country in the northwest. It is, however pleasant to sit in the sun in sheltered places.

The small croaking frogs are now generally heard in all those stagnant ponds or pools in woods floored with leaves, which are mainly dried up in the summer. At first, perhaps, you hear but one or two dry croaks, but, if you sit patiently, you may hear quite a concert of them at last,— er-wah er-wah er-wah, with a nasal twang and twist,— and see them dimpling the surface there and there by their movements. But if you approach the pond-side, they suddenly cease. We hear them at J. P. Brownes Pond, which is edged with ice still on the north. The water must be smooth and the weather pretty warm.

There is still some icy snow in hollows under the north sides of woods.