The limerick form was popularized by Edward Lear in his first "Book of Nonsense" (1846) and a later work, "More Nonsense, Pictures, Rhymes, Botany, etc". (1872). Lear wrote 212 limericks, mostly considered nonsense literature. It was customary at the time for limericks to accompany an absurd illustration of the same subject, and for the final line of the limerick to be a variant of the first line ending in the same word, but with slight differences that create a nonsensical, circular effect. The humour is not in the "punch line" ending but rather in the tension between meaning and its lack.