Mark Twain Did Not Suffer Fools (or "Idiots of the 33rd Degree") Gladly

Over a century ago, a crook tried to sell Mark Twain some medicine. Worse, this person claimed the medicine cured two diseases (diphtheria and meningitis) that had killed two of Twain's kids.
The enraged author sent this note back to the scoundrel:

Nov. 20. 1905

J. H. Todd
1212 Webster St.
San Francisco, Cal.

Dear Sir,

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...