"Nonsensia."  From The Scarlet Letter yearbook (Rutgers, 1918).

"The boy who could talk nonsense."  From The Laughing Prince by Parker Fillmore and illustrated by Jay Van Everen, 1921.

The importance of nonsense, from the Davenport Daily Republican, Feb. 17, 1901.  (Via Yesterday's Print.)

From The Scarlet Letter yearbook (Rutgers, 1915).

"The body is said to have only five senses, but the greatest sense of all is omitted.  Nonsense!"  From The Harvard Lampoon, 1921.

A Defence of Nonsense by G. K. Chesterton, 1911.

From The Scarlet Letter yearbook (Rutgers, 1912).

Talking through his hat.  From Die Bühne, 1925.

Jonathan reports: "In a novel from 1930 [The French Powder Mystery], Ellery Queen (the author and, as it happens, the character) mentions a book on a shelf: Nonsense Anthology, by A. I. Throckmorton. As far as I can tell, this is a fictitious nonsense anthology!"

The context of this still from the spoof mystery series 33 Minute Detective (33分探偵) is that a murder victim typed out his killer's name in his dying moments, but the detective, in order to comedically stretch out an obvious case to fill up the show's half-hour time slot, posits that the keyboard was set to romaji (the Romanized transliteration of Japanese), so that the actual hiragana word was nonsense.

Philosopher Gilles Deleuze suggests that there's a one-of-a-kind sort of nonsense in the magic word abraxas: it is an immobilized "pure thought" and the "highest finality of sense," like a seemingly-nonsensical one-word simile, the paradoxical conclusion of an infinite regression of propositions (a is like b, and b is like c, and c is like d, and so on forever).  "There is only one kind of word which expresses both itself and its sense—precisely the nonsense word: abraxas" (Difference and Repetition [1995]).

Here's some perfect nonsense from Judy, Or The London Serio-Comic Journal, 1869.

"Yes—yes—to be sure.  That is to say—nonsense."  From Judy, Or The London Serio-Comic Journal, 1873.

Here's a "pack of nonsense" from Judy, Or The London Serio-Comic Journal, 1873.

We call hogwash where we find it.  There's a probability puzzle popularly called the "Monty Hall Problem."  Entire books have been written about it, but we feel compelled to establish that it is pure nonsense.  A contestant on Let's Make a Deal declares a choice from three doors (two hiding goats and one a new car).  Then the host reveals a goat behind a door not chosen and suggests the possibility of switching to the other remaining door.  On paper, this is a counterintuitive paradox in which the contestant is convinced of a 50/50 chance of success, when in fact switching doors offers demonstratively better odds.  However, theorizing about the puzzle is ludicrous, and the considerable debate over the years is meritless, for the simple reason that a game show is a piece of theatre tantamount to a magic trick.  The host of this purported gambling scenario obviously works for "the house" and knows where the car is hidden (presuming—which one cannot, in fact—that the car is not moved from door to door behind the scenes).  Based upon subtle facial expressions and tones of voice (neither of which can be tabulated mathematically), the contestant wonders about being manipulated (with good reason).  Creating truth tables or running simulations of possible outcomes is meaningless because there is no circumstance in the real world where any of the probability theory could possibly be relevant.  There's a reason why the game show does not allow the contestant to simply walk up to a door and open it to determine the outcome.  Just as a magician displays a deck to prove that it's well-shuffled (which it isn't, and that's why pains are taken to prove otherwise), the host opens a door with a goat as part of an elaborate psychological and theatrical presentation that "proves" the outcome is random.  The outcome is not random on a television show designed to entertain.  The contestant wins if the powers that be wish to give away a car during that episode, period.  There is no other conceivable consideration (sorry, mathematicians and statisticians!).  While we tip our hat to those who are capable of modeling possible scenarios ad nauseam, the "Monty Hall Problem" is no problem at all.