It was on March 6, 1846, he particularly observed the potability of Walden, as well as its temperature: 42°, one degree less than water from "one of the coldest wells in the village." This fortuitous coolness stayed true in the summer, as Thoreau notes in Chapter IX, "Walden never becomes so warm as most water which is exposed to the sun, on account of its depth." The water, he adds, does not have the additional taste that comes from a town pump.
Walden was more than just Thoreau's water source, it also provided a food source. In his next paragraph, he notes the fish there. Much as he did with the water itself, he also describes these fish in superlative terms: their great size, speed, and variety. He mostly engaged in catching pickerel, including ice fishing for them in the winter. Going into the water might change one's perception of it: At first appearing black of dark brown, it seems yellowish once inside. But, he notes, "this water is of such crystalline purity that the body of the bather appears of an alabaster whiteness."The shape of the pond along the shore, he notes, "is irregular enough not to be monotonous." Later in the chapter, Thoreau included a short poem:
It is no dream of mine,
To ornament a line;
I cannot come nearer to God and Heaven
Than I live to Walden even.
I am its stony shore,
And the breeze that passes o'er;
In the hollow of my hand
Are its water and its sand,
And its deepest resort
Lies high in my thought.
For Thoreau, living at Walden was a spiritual experience of exploring his own nature as well as the nature around him. His friend, poet Ellery Channing, once remarked that The Walden Pond Society was one of the local places of worship. Thoreau ended the experiment after two years, two months, and two days. Contrary to popular assumption, however, his book Walden was not written at the pond. Instead, he was working on his earlier book, A Week on the Concord and Merrimack Rivers. Walden would not be published for another 8 years after his March 6, 1846 observation of water.
Today, visitors still can visit and observe Walden Pond as well as a recreation of Thoreau's house there, and have a spiritual experience of their own. Much like Thoreau did in the 1840s, they can also go swimming there (though it's not clear if drinking the water is recommended).