He thought he saw among his books
A peeping thesaurus
He looked again and found it was
A sleeping tyrannosaurus
“If it wakes up now,” he sighed
I’ll surely miss my bus.”

Alternative Version

He thought he saw the library shelves
Were packed with thesauri
He looked again and found they were
All sleeping tyrannosauri
“If they should wake up now,” he sighed
I shan’t again be I.”