A commenter, Joshua, on an earlier post was surprised to learn that the "frog in a well" story came from Chuang Tzu.  Perhaps this is new to other readers out there; so, let me excerpt the relevant passage from Chapter 17 from Watson’s translation of The Complete Works of Chuang Tzu (pp. 185-187).  There might be other sources or versions of this story – please let me know if you have another citation…

Kung-sun Lung [the famed logician] said to Prince Mou of Wei [a published Taoist], "When I was young I studied the Way of the former kings, and when I grew older I came to understand the conduct of benevolence and righteousness… [he goes on to mention his other intellectual accomplishments]… But now I have heard the words of Chuang Tzu and I am bewildered by their strangeness.  I don’t know whether my arguments are not as good as his, or whether I am no match for him in understanding.  I find now that I can’t even open my beak.  May I ask what you advise?

Prince Mou leaned on his armrest and gave a great sigh, and then he looked up at the sky and laughed, saying, "Haven’t you heard about the frog in the caved-in well?  He said to the the great turtle of the Eastern Sea, ‘What fun I have!  I come out and hop around the railing of the well, or I go back in and take a rest in the wall where a tile has fallen out.  When I dive into the water, I let it hold me up under the armpits and support my chin, and when I slip about in the mud, I bury my feet in it and let it come up over my ankles.  I look around at the mosquito larvae and the crabs and polliwogs and I see that none of them can match me.  To have complete command of the water of one whole valley and to monopolize all the joys of a caved-in well – this is the best there is!  Why don’t you come some time and see for yourself?’

"But before the great turtle of the Eastern Sea had even gotten his left foot in the well his right knee was already wedged fast.  He backed out and withdrew a little, and then began to describe the sea.  ‘A distance of a thousand li cannot indicate its greatness; a depth of a thousand fathoms cannot express how deep it is.  In the time of Yu there were floods for nine years out of ten, and yet its waters never rose.  In the time of T’ang there were droughts for seven years out of eight, and yet its shores never receded.  Never to alter or shift, whether for an instant or an eternity; never to advance or recede, whether the quantity of water flowing in is great or small – this is the great delight of the Eastern Sea,’

"When the frog in the caved-in well heard this, he was dumbfounded with surprise, crestfallen, and completely at a loss.

[The narrator then shifts back to the Kung-sun Lung-Prince Mou conversation]. 

"Now your knowledge cannot even define the borders of right and wrong and still you try to use it to see through the words of Chuang Tzu – this is like trying to make a mosquito carry a mountain on its back or a pill bug race across the Yellow River.  You will never be up to the task!

"He whose understanding cannot grasp these minute and subtle words [of Chuang Tzu], but is only fit to win some temporary gain – is he not like the frog in the caved-in well?…"