To be specific, it’s the original contract between Harper&Brothers — one of the ancestor firms of current publisher HarperCollins — and Herman Melville for Moby-Dick.

Publishing contracts haven’t changed all that much since then; they’ve just gotten longer and more complex.  Melville, wisely, had representation, in the person of his-brother-the-lawyer.  (Literary agents in the modern sense — if Wikipedia is to be believed — didn’t become common until the 1880’s, and Moby-Dick was published in 1851.)