Clemens was a heavy smoker, consuming between twenty and forty cigars a day. His only rule, as he joked on his seventieth birthday, was "never to smoke more than one cigar at a time."
Smoking not only brought him pleasure, it was essential for his creative process. After (temporarily) giving up the habit while writing Roughing It in 1871, he found himself "seriously obstructed."
He could not refrain from smoking even as a houseguest. When visiting Hartford for the first time in1868 he noted, "I have to smoke surreptitiously when all are in bed, to save my reputation, and then draw suspicion upon the cat when the family detect the unfamiliar odor. . . . So far, I am safe; but I am sorry to say that the cat has lost caste."