SOLVED. Humorous novel with discussion of Thoreau. [s]

[Rosa]

Several years ago--at least three, maybe five--my father read a short passage to me from this book. A not-too-bright substitute teacher (I think he was a sub) was discussing with the class the quote of Thoreau's, "I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion."
Then (I think) a student pointed out that Thoreau also said something positive about chairs and something negative about pumpkins (I forget what).
The sub said something like, "Very good point!" Then he wrote on the board, "Order of Thoreau's seating preferences--chair > pumpkin > cushion."
Does anyone know which book this is from?

[Ayshe]

That's Not a Feeling appears to have similar scene: https://books.google.com/books?id=6fW...

[Rosa]

Excellent! Thank you, Ayshe.