How do you cite a quote in your fiction

[alhawke]

I'm quoting John Donne, a sixteenth century poet, in my new book. For those of you who've quoted writers, where do you guys place the source? Should I add it at the end of the book somewhere or on the same page as the quote (with a superscript #)??

[Post-Crisis D]

Are you quoting with an attribution?  Is it in dialogue?  Is it to open a chapter?  How is it used?

Depending on how exactly you are using it and incorporating it into your story, I wouldn't do a footnote on the same page as this is fiction, not non-fiction.  A footnote or superscript would pull the reader out of the story.  I'd identify the source in an acknowledgments chapter at the end of the book.

[alhawke]

It's a single sentence from a poem being quoted by a witch in the story in dialogue. Do I even have to source it?

[Post-Crisis D]

Unless it falls under some exception somewhere, it should be public domain.  For something that old, you probably don't have to list the source.  If there are different versions, then you may want to acknowledge which source you used in your acknowledgments.

You should credit the line to John Donne somewhere.  Even though it is likely public domain, if you don't credit Donne somewhere, you could be accused of plagiarism which is a separate issue from copyright.

[Bill Hiatt]

That's good advice. Always err on the side of caution.

[Jeff Tanyard]

It's a single sentence from a poem being quoted by a witch in the story in dialogue. Do I even have to source it?

If it's obvious the witch is quoting someone else, then I wouldn't bother with attribution for a public domain quote.

Here's an example from The Forever War where a line from a Robert Burns poem is quoted by one of the characters:

"Filters up." Gray haze of smoke and dust. Clods of dirt falling with a sound like heavy raindrops.

"Listen up: 'Scots, wha hae wi' Wallace bled; Scots, wham Bruce has aften led, Welcome to your gory bed, Or to victory!'"

I hardly heard him for trying to keep track of what was going on in my skull. I knew it was just post-hypnotic suggestion, even remembered the session in Missouri when they’d implanted it, but that didn’t make it any less compelling.

I don't think Burns's name was ever mentioned in the book, but it's public domain stuff that is obviously being quoted by a character rather than being the character's own original words, so it doesn't really matter.