Thoreau's Journal: 14-Jun-1857
B.M. Watson tells me that he learns from pretty good authority that Webster once saw the sea-serpent. It seems it was first seen, in the bay between Manomet and Plymouth Beach, by a perfectly reliable witness (many years ago), who was accustomed to look out on the sea with his glass every morning the first thing as regularly as he ate his breakfast. One morning he saw this monster, with a head somewhat like a horse’s raised some six feet above the water, and his body the size of a cask trailing behind. He was careering over the bay, chasing the mackerel, which ran ashore in their fright and were washed up and died in great numbers. The story is that Webster had appointed to meet some Plymouth gentlemen at Manomet and spend the day fishing with them. After the fishing was [over], he set out to return to Duxbury in his sailboat with Peterson, as he had come, and on the way they saw the sea-serpent, which answered to the common account of this creature. It passed directly across their bows only six or seven rods off and then disappeared. On the sail homeward, Webster having had time to reflect on what had occurred, at length said to Peterson, “For God’s sake, never say a word about this to any one, for if it should be known that I have seen the sea-serpent, I should never hear the last of it, but wherever I went should have to tell the story to every one I met.” So it has not leaked out till now.