Documents from the Vatican's secret archive are set to be opened in an exhibition in Rome, sponsored by IT vendor EMC.

Around 100 documents, including a letter written by Marie Antoinette when she was in prison in 1793, will be shown to the public. The 'Lux in Arcana' exhibition is taking place in the Musei Capitolini in Rome, and runs until September.

EMC said its sponsorship was part of its Information Heritage initiative, in which it has been digitising historic documents and making them publicly available.

The letter by Marie Antoinette is thought to have been addressed to Louis XVI's brother Charles Philippe, Count of Artois, who in 1824 became Charles X, King of France.

The letter, which is only ten lines in length, is handwritten and reads, "The sentiments of those who share my pain, my dear brother-in-law, are the only consolation I can receive in this sad circumstance." The letter is then signed, "Your loving Sister-in-Law and Cousin Marie Antoinette."

Other documents date from the eighth century through to the twentieth century, and include a letter from the British Parliament to Pope Clement VII about King Henry VIII's impending divorce, and a letter written on birch bark by Native Americans to Pope Leo XIII.