I found a quote of Edmund Burke trashing William Godwin:
'Pure defecated Atheism', said Burke [of Godwin], 'the brood of that putrid carcase the French Revolution.'
I was especially interested because I'd been unable to find any other direct quote of Burke saying negative things about Godwin. People claim Burke disliked Godwin, but I have my doubts and have searched for the evidence that those people never provide.
So I tracked down the citations, and ultimately the quote is unsourced. While doing that, I found another quote of Burke trashing Godwin which also turned out to be unsourced.
I also contacted an academic expert who agreed the quote is fake.
Here's what I looked up:
The defecated atheism quote is from Godwin's Moral Philosophy: An Interpretation of William Godwin by D. H. Monro.
I originally found it in a different Godwin paper which didn't even try to source it.
Monro says it's quoted from Ford K. Brown, Life of William Godwin (London, 1926), p 155
So I got that book. It has the quote along with a footnote. The footnote states:
Edmund Burke, who is also said to have called Godwin "one of the ablest architects of ruin." (Gilfillan's Literary Portraits (First Series, Edinb. 1845), p.16.)
I found the Literary Portraits book. On page 16 it has the architect of ruin quote, unsourced. It doesn't have the defecated atheism quote at all.
It's no good to source a quote to a secondary source without following the citations back to an adequate source. That spreads myths.