George Washington's original proclamation establishing the first federal Thanksgiving Day is set to break records at Christie's on November 14.

The proclamation could become the most valuable American book or document ever sold at auction

The document, signed by Washington on October 3, 1789, is valued at an impressive $8m-12m.

Should it meet its high estimate, it will top the record for any American book or historic document at auction, which was set at $9.8m by Washington's personal copy of the Acts of Congress at Christie's in June 2012.

The piece sees Washington calling for the last Thursday of November to be designated Thanksgiving Day, stating, "Both Houses of Congress have by their joint Committee requested me to recommend to the People of the United States a day of public thanksgiving and prayer".

"Now therefore do I recommend and assign Thursday the 26th day of November next to be devoted by the People of these States to the service of that great and glorious Being…That we may then all unite in rendering unto him our sincere and humble thanks--for... the great degree of tranquility, union, and plenty, which we have since enjoyed.

"For the peaceable and rational manner, in which we have been enabled to establish constitutions of government for our safety and happiness, and particularly the national One now lately instituted--for the civil and religious liberty with which we are blessed; and the means we have of acquiring and diffusing useful knowledge..."

Prior to the sale, the proclamation will tour the US, beginning in Los Angeles on October 17 and ending at Christie's New York galleries on November 7-13.

Paul Fraser Collectibles has some wonderful historical manuscripts for sale, including a rare copy of the Declaration of Independence.