This pun is by Lewis Carroll.
“And how many hours a day did you do lessons?” said Alice, in a hurry to change the subject.
“Ten hours the first ‘day,,” said the Mock Turtle. “Nine the next., and so on.
“What a curious plan!” exclaimed Alice.
“That’s the reason they’re called lessons,” the Gryphon remarked. “Because they lessen from day to day.”