“All these flat earth guys!… Here's the Hovind theory on the flat earth… I suspect, I do not know this, I just have a sneaking suspicion that some atheists someplace have got in a club together to say "Hey, let's start pushing this idea that the earth is flat, and let's see if the Christians fall for it." They've done that several times before over the last hundred years, spread some stupid idea and sometimes a lot of Christians do fall for it… And then they'll use that to sit around and laugh and say "Wow, look at how stupid these Bible-believers are!"”

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

The Zebra
How to Tell Your Friends from the Apes (1931)

"Geoffrey Rush interview" http://www.virgin.net/movies/interviews/geoffreyrush2.html.

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.

Interview with the Texas Tribune https://www.washingtonpost.com/news/the-fix/wp/2015/03/25/ted-cruz-compares-climate-change-activists-to-flat-earthers-where-to-begin/, Washington Post (March 24, 2015)
2010s