Perry's Index to the Aesopica
Fables exist in many versions; here is one version in English:
AESOP AND THE BOW
When a certain man of Athens saw Aesop playing with marbles amidst a crowd of
boys, he stood there and laughed at Aesop as if Aesop were crazy. As soon as
he realized what was going on, Aesop -- who was an old man far more inclined
to laugh at others than to be laughed at himself -- took an unstrung bow and
placed it in the middle of the road. 'Okay, you know-it-all,' he said, 'explain
the meaning of what I just did.' All the people gathered round. The man wracked
his brains for a long time but he could not manage to answer Aesop's question.
Eventually he gave up. Having won this battle of wits, Aesop then explained,
'If you keep your bow tightly strung at all times, it will quickly break, but
if you let it rest, it will be ready to use whenever you need it.'
In the same way the mind must be given some amusement from time to time,
so that you will find yourself able to think more clearly afterwards.
Aesop's Fables. A new translation by Laura
Oxford University Press (World's Classics): Oxford, 2002.
cover, with new ISBN, published in 2008; contents of book unchanged.
Perry 505: Gibbs (Oxford) 537 [English]
Perry 505: Phaedrus 3.14 [Latin]
You can find a compilation of Perry's index to the Aesopica in the gigantic appendix to his
edition of Babrius and Phaedrus for the Loeb Classical Library
(Harvard University Press: Cambridge, 1965). This book is an absolute must for anyone interested
in the Aesopic fable tradition. Invaluable.