A letter written by Mary Queen of Scots is expected to fetch £3000 when it goes under the hammer later this month.
It was discovered in Blair Castle in Ayrshire and has been verified as being written by the Queen.
The 450-year-old letter, dated March 20, 1554, relieves the Laird of Blair from his duties at court as he was suffering from gout.
It is part of the largest house sale in Scotland in over a decade, with over 1000 items up for sale at the auction in Edinburgh on March 14 and 15.
Blair Castle is the oldest continually inhabited mansion in Scotland and home to the Barony of Blair. The family traced their ancestry back to William the Lion in 1165.
Other items up for sale include an exercise machine from the early 19th century, a pair of silver dog collars from 1815 and a rare Zeigler carpet.
Luke and Caroline Borwick have lived in the castle for the last 11 years but have recently sold it so they can spend more time with their grandchildren in London.
Mrs Borwick said "It’s a wonderful place, full of wonderful things, but sadly as we have sold the Castle we cannot take them with us.
"Obviously we hope that every single item goes to someone who will treasure them as much as we have. We are merely custodians of these beautiful things and it is time, after 900 years, to pass the responsibility on to others."
The items are being sold by auctioneers Lyon & Turnbull.
Gavin Strang from the company said "The sale has a total estimate of £500,000 and is a unique glimpse at Scottish history through the ages, it inncludes things from ‘above and below stairs’ making this the ‘sale of the century’, as nothing has been sold by the family for over 900 years.
"This will be one of the more exciting sales of 2012, as all the items in the sale including antiques, paintings, silver and books are fresh to the market. We have 900 years of history for sale. As with any good Country House Sale there will be pieces long forgotten, that we have uncovered in the attics and cellars of the Castle."