"Watson had a colt born about ten or eleven the last evening. I went out to see it early this morning, as it lay in the cold pasture. It got up alarmed and trotted about on its long, large legs, and even nibbled a little grass, and behaved altogether as if it had been an inhabitant of this planet for some years at least. They are as precocious as young partridges. It ran about most of the day with its mother. Watson was surprise to see it so much larger than the night before. Probably they expand at once on coming to the light and air, like a butterfly that has just come out of its chrysalis."
HD Thoreu's Journal: June 14, 1857