“Our imagination flies -- we are its shadow on the earth.”

"Imagination" in America Sings (1949); re-published in Pearls From Peoria (2006)

On Dreams

Callum Coats: Water Wizard
Callum Coats: Water Wizard
Variant: "Our primeval Mother Earth is an organism that no science in the world can rationalize. Everything on her that crawls and flies is dependent upon Her and all must hopelessly perish if that Earth dies that feeds us." (Callum Coats: Water Wizard)

The Man With the Blue Guitar (1937)
Context: Do not speak to us of the greatness of poetry,
Of the torches wisping in the underground,
Of the structure of vaults upon a point of light.
There are no shadows in our sun,
Day is desire and night is sleep.
There are no shadows anywhere.
The earth, for us, is flat and bare.
There are no shadows.

Book Three, Chapter XI.
Democracy in America, Volume II (1840), Book Three

Often cited as by Auden without attribution, this quotation has been traced to John Foster Hall (1867-1945), an English comedian known as the Reverend Vivian Foster, Vicar of Mirth. Full history with sound recording http://audensociety.org/vivianfoster.html
Misattributed

The Universe - Sex in Space (2008)

Source: By the River Piedra I Sat Down and Wept

This quotation is often found on the internet attributed to Magellan, but never with a source, and no English occurrence prior to its use by Robert Green Ingersoll in his essay "Individuality" http://www.infidels.org/library/historical/robert_ingersoll/individuality.html (1873) has been located. Thus, it it most likely spurious. In that essay Ingersoll states:
It is a blessed thing that in every age some one has had individuality enough and courage enough to stand by his own convictions, — some one who had the grandeur to say his say. I believe it was Magellan who said, "The church says the earth is flat; but I have seen its shadow on the moon, and I have more confidence even in a shadow than in the church." On the prow of his ship were disobedience, defiance, scorn, and success.
Disputed
Variant: The Church says that the Earth is Flat, but I know that it is Round. For I have seen its Shadow on the Moon and I have more Faith in a Shadow than in the Church.
Source: As quoted in Oxford Academic (25 July 2013) http://oupacademic.tumblr.com/post/56463634957/misquotation-i-have-seen-the-shadow-of-the-earth