The only surviving copy of the Declaration of Arbroath is expected to go on public display later this year.
Earls and barons gave the declaration their seal of approval
The frail condition of the document, drafted in 1320, has prevented it being exhibited in recent years.
But experts are working on a special case which should allow it to feature in an exhibition marking the 700th anniversary of William Wallace's death.
The document, held in the National Archives of Scotland, should go on show at the Scottish Parliament from August.
It is hoped that the "For Freedom Alone" exhibition will also feature the only surviving document issued by Wallace, a letter to the people of Lubeck and Hamburg.
The exhibition's title is taken from the wording of the Declaration of Arbroath, which has been described as the country's best-known historical document.
The letter was sent to the Pope by eight Scottish earls and 38 barons, calling on him to recognise Scotland's independence and acknowledge Robert the Bruce as king.
The document is thought to have been drafted by Bernard, the abbot of Arbroath, during the war of independence with England.
It was sent to the Pope six years after the battle of Bannockburn, where Robert the Bruce defeated the English.
The document contains the lines: "As long as but a hundred of us remain alive, never will we on any conditions be brought under English rule.
"It is in truth not for glory, nor riches, nor honours, that we are fighting, but for freedom - for that alone, which no honest man gives up but with life itself."
Four years after the declaration, Rome recognised Robert the Bruce as king.
The only surviving copy of the document was held at Edinburgh Castle until the early 17th Century, when it was moved to Tyninghame for safe keeping while work was done at the castle.
However, damp caused damage to the document before it was returned to the National Archives of Scotland in 1829.
The National Archives of Scotland contacted Dr Shin Maekawa, senior scientist at the Getty Conservation Institute in California, more than a decade ago seeking information and advice.
Out of that has grown the project to re-house the manuscript in a hermetically sealed case filled with inert gas to create an environment with greatly reduced oxygen.
It will be built to the Getty design by a team from the mechanical and chemical engineering department at Heriot-Watt University, Edinburgh.
The aim is to preserve the manuscript for future generations by slowing down the effects which can cause organic material like parchment to deteriorate.
These include air pollution, changes in temperature and humidity, and attacks by bacteria, fungi and insects.
George MacKenzie, the Keeper of the Records of Scotland, said: "This document is one of the most important manuscripts cared for by NAS and extensive research, great care and consideration has and will always be given to ensure the long-term preservation of this irreplaceable manuscript.
"Regular exhibition of this fragile document will never be possible, but this important project may allow its very occasional display in the future."
The declaration, which was drawn up on 6 April, is the featured document on the National Archives of Scotland's website this month.