I'm a little late in posting this, but it's too awesome to pass: Shaun Usher's Letters of Note has a copy of a 1905 letter sent by Mark Twain to a patent medicine salesman who tried to sell bogus medicine. Twain was furious to have received the pitch as he was recently widowed after his wife suffered heart failure:
Your letter is an insoluble puzzle to me. The handwriting is good and exhibits considerable character, and there are even traces of intelligence in what you say, yet the letter and the accompanying advertisements profess to be the work of the same hand. The person who wrote the advertisements is without doubt the most ignorant person now alive on the planet; also without doubt he is an idiot, an idiot of the 33rd degree, and scion of an ancestral procession of idiots stretching back to the Missing Link.