Hidden in a dusty trunk in an abandoned and looted Englewood home, the papers of Harvard’s first black graduate, Richard T. Greener, had long been thought lost to history.

So when the Sun-Times reported last year that 52-year-old contractor Rufus McDonald found them while clearing out an attic near 75th and Sangamon, he was praised as a hero who’d unearthed forgotten details of a pioneering African-American intellectual’s life.

Several museums and Harvard University itself expressed a keen interest in the historically significant 140-year-old Greener documents. An excited Gates, who leads Harvard’s W.E.B. DuBois Institute for African-American Research, even said the discovery gave him “gooseflesh.”

But now McDonald says the irreplaceable collection could go up in flames — literally.

McDonald — who recently sold just two of the documents for $52,000 to the University of South Carolina, where Greener also studied and taught — is threatening to torch the rest unless Harvard offers him more cash.

“I’ll roast and burn them,” an angry McDonald said Tuesday, saying Harvard offered an “insulting” $7,500 for a collection that includes Greener’s 1870 Harvard diploma and was appraised at $65,000.

The article does not say how many tea party rallies the man has attended in the past.