A copy of the influential collection of principles, the Magna Carta, will go on sale through Sotheby's. This is not just any copy, but one signed by King Edward I in 1297, which became the operative version, the one that was entered into English common law and became the law of the land, although frequently ignored.

However, its human rights provisions, most notably the right of Habeas Corpus, meaning that people had rights against unlawful imprisonment, eventually made their way into modern day constitutional law.

"When it's something as enormously important as this, you try to get a handle on it," Sotheby's vice chairman David Redden said. "It is absolutely correct to say the Magna Carta is the birth certificate of freedom. It states the bedrock principle that no person is above the law — that is the essence of it."

That's a stretch, as is his other far-fetched claim that one copy of the two Magna Carta outside Britain is "the most important document in the world." However, Mr. Redden can't be blamed for doing his best of reaching the record $20-30 million his company seeks for the document, on behalf of the seller.

Written in medieval Latin on sheepskin, the Magna Carta was owned for five centuries by a British family. Sometime during the early 1980s, they put it up for sale and a few years later emerged at the National Archives in Washington, joining the Declaration of Independence and the U.S. Constitution.

The document is currently owned by billionaire Ross Perot, who purchased it for $1.5 million in 1984 from the British Brudenell family, earls of Cardigan. The proceeds of the sale will allegedly benefit the Perot Foundation. It is the only Magna Carta in private hands, of the 17 available copies.

In 1215, it was forged under pressure from barons out of outrage against the abuses of King John, a somewhat cruel and abusive sovereign.