Here is fable 181 (p. 134), from:
 
Aesop, 1998, The complete fables (translated by Olivia and Robert Temple):
New York, etc., Penguin Books, xxv + 262 p.
 
"The Dog and the Shellfish
 
There was a dog who used to swallow eggs. One day he saw a shellfish. He
opened his mouth and snapped his jaws shut again violently, swallowing it,
because he thought it was an egg. But, feeling a heaviness in his bowels,
he became ill and said,
        'I only got what I deserve--I, who assume that everything round is an
egg.'
 
This fable teaches us that those who undertake things recklessly get
themselves into strange predicaments."
 
Aesop lived more than 2500 years ago.
 
Andrew K. Rindsberg
Geological Survey of Alabama