A MANUSCRIPT written by Mary, Queen of Scots shortly before her execution is to be sold at auction in the US.

The document, dating to when she was considered such a threat to the English throne she was held captive, is to go on sale with bidding set to start at $1,000 (£600).

It relates to her appointment of a captain to a castle connected with an infamous massacre.

Bobby Livingston, of the auctioneers RR Auction, said: "The document dates to near the end of Mary's life while she was imprisoned at Chartley Castle in Staffordshire by her cousin, Queen Elizabeth I of England."

Four months after signing the document, Mary was implicated in the Babington Plot to assassinate Queen Elizabeth and assume her place on the throne and she was put to death by beheading on February 8, 1587. The letter is from the time when Mary was granted the right to the profits of Wassy in the Champagne region of France as part of her rights as widow of Francis II and the funds were being managed on her behalf by her uncle Francis, Duke of Guise.

In 1562, Wassy was the site of the notorious massacre of Huguenots by troops under Francis, and sparked the bloody French Wars of Religion. The recipient of the post of guarding the castle in the letter, Jacques de la Montaigne, was undoubtedly present at the massacre and is described by one source as its "author and solicitor".

The one-page vellum manuscript in French, dated April 30, 1586, reads: "Mary, as queen of Scotland and dowager queen of France, grants, on the 'specialle recommenda[ci]on' of her cousin [Henri], duc de Guise, the captaincy of the castle of Wassy to the duke's maitre d'hotel, [Jacques] de la Montaigne."

It is signed below by Mary and countersigned by her secretary of state, Claude de la Boissiliere Nau.

Also going on sale at the auction next month in Boston, Massachusetts, is Nelson Mandela's Freedom Torch used during a 1994 ceremony for a minimum £30,000 and a photograph of Albert Einstein sticking out his tongue for £6,000.