The scribes who 772 years ago wrote the Magna Carta for King John of England were drafting a document that is the basis for individual rights of Americans today. Tomorrow that document will be on exhibit in Alexandria.

The traveling exhibit of the Magna Carta, on loan from the Lincoln Cathedral in England, will be at the Lyceum at 201 S. Washington St. from 10 a.m. to 6 p.m. tomorrow. Tickets are required and can be picked up at no charge at the Lyceum beginning at 9 a.m.

The exhibit, titled "Roads to Liberty: Magna Carta to the Constitution," was formally launched March 11 at a reception in the White House Rose Garden with President Reagan. When the tour ends Sept. 18 in Philadelphia, it will have been to 25 states and the District of Columbia. It is housed in a 40-foot trailer.

"There are about 20 different collectors who have loaned documents to the tour," explained Fred Biebel, chairman of the tour and a member of the U.S. Constitution Bicentennial Commission. Each state historical society or bicentennial commission displays state documents when the exhibit is in its state.

Virginia documents on exhibit, which are all facsimiles, include the September 1787 edition of the Virginia Gazette, the first newspaper to print the constitution in Virginia, the 1621 charter that established the Virginia House of Burgesses, which became the General Assembly, and Virginia's ratification of the U.S. Constitution, which passed by a vote of 89 to 79 on June 25, 1788.

Historians are not sure how many original copies of the Magna Carta were drafted for King John in 1215 in Runnymede, England, but most agree 11 to 14 copies were made. The Magna Carta spells out rights demanded by the king's barons.

"Only four copies have survived of the Magna Carta made in 1215 and the one in the best condition is the Lincoln Cathedral copy," said A.E. Dick Howard, a professor of constitutional law at the University of Virginia. Howard is chairman of the Virginia Commission on the Bicentennial of the United States Constitution and is a member of the U.S. Constitution Council.

According to Howard, 17 copies of the Magna Carta drafted from 1215 to 1297 survive. All but one of the copies are in England. In 1984 Texas billionaire H. Ross Perot paid an English family $1.5 million for a 1297 copy of the Magna Carta, drafted for King Edward I.

The Lincoln Cathedral Magna Carta "is the oldest historical document to which one would trace the liberties found in the U.S. Constitution," Howard said.

"There are several provisions in the Magna Carta that are distinctly constitutional in a modern sense," Howard said. "The provisions that proceedings be conducted according to the law of the land, which in a modern sense is our conception of due process of law in the Fifth and 14th amendments {of the Constitution} can be traced right back to the Magna Carta."

Howard added that the ban on cruel and unusual punishment for a crime, as outlined in the Eighth Amendment of the Constitution, "can be traced to a principle in the Magna Carta that punishment should be proportionate to the crime."

There is another side to the traveling exhibit, which includes several other historic documents as well as copies of the Constitution and Bill of Rights, and that is the extraordinary security and physical measures required to protect the priceless documents.

The exhibit never leaves a 40-by-8 foot specially converted trailer, valued at $1 million, which expands to a width of 13 feet. The documents are displayed in five bulletproof cases, designed by the Smithsonian Institution. All exhibit documents, except the Magna Carta, are insured by Lloyds for $4 million. Biebel said the Magna Carta is insured by a federal law that protects foreign documents on loan to the United States.

"The trailer has the finest fire prevention system available," Biebel said. " . . . We keep a constant temperature in the trailer of 62 degrees, it is air conditioned and heated, and we keep a constant humidity level of 55 percent." The trailer also has special low-level lighting.

When the trailer is on the road, it gets a state police escort, and it is under 24-hour police protection. "We are also under constant surveillance by a satellite provided by a private protection company," Biebel said. About 300,000 people have seen the exhibit.

He estimates that corporate sponsor American Express Co. will spend more than $2 million on the exhibit. The exhibit also is sponsored by the Commission on the Bicentennial of the U.S. Constitution, the U.S. Constitution Council of the Thirteen Original States Inc. and local organizations.

The exhibit will be in Annapolis Sunday, Baltimore Monday and Tuesday, Rockville Wednesday and Sept. 3, Hagerstown Sept. 4, and at the U.S. Capitol Sept. 14 to 16.