In 16th-century Mexico, sisters Isabel de Carvajal de Andrade and Leonor de Carvajal were strangled with iron collars and burned at the stake.

Their crime — practicing Judaism.

U.C. Berkeley's Bancroft Library recently acquired thousands of pages of documents — until now thought lost or destroyed — detailing testimony in the sisters' trial. The documents are part of an extensive collection of original rare records from the Mexican Inquisition, which lasted from 1570 until the end of the Spanish colonial period in the early 1800s.

An arm of the Spanish Inquisition, the Mexican Inquisition was launched by the Catholic Church to maintain religious orthodoxy in the face of what the church viewed as the Protestant menace.

Though much of its energy went toward preventing sexual misconduct, especially among clergy, the Holy Office of the Mexican Inquisition occasionally focused on prosecuting crypto-Jews. Those Jews had supposedly converted to Christianity but were suspected of maintaining their heritage by practicing Jewish rites in secret.

The Carvajal family — of which the two sisters were a part — was one of the most famous of the crypto-Jewish families to be prosecuted in 16th-century colonial Mexico.

Perhaps the most prominent Carvajal was Luis de Carvajal, declared governor of the province of Nuevo León in 1579. In 1596, at the height of the Inquisition's fervor against crypto-Jews, he was declared a heretic and burned alive along with his mother and five sisters.

Around the same time, Carvajal's nephew and namesake, Luis de Carvajal "El Mozo" (the younger), was accused of relapsing into Judaism. Buckling under torture, he handed over to his inquisitors 116 names of other "Judaizers," including his mother and two of his sisters. He was ultimately burned at the stake alongside them.

Trial documents found in the recent U.C. Berkeley acquisition reveal that evidence against the sisters included their use of clean clothing and bed linens on Friday evenings — factors used to prove their observance of Shabbat. Their fasting and dietary restrictions and participation in secluded gatherings were also cited.

A similar case included in the U.C. Berkeley acquisition concerns Manuel de Lucena, a Portuguese associate of the younger Luis de Carvajal, tried and convicted for being a crypto-Jew.

"These are famous, famous cases," said Walter Brem, Bancroft Library's Latin-American curator. "In the historiography of crypto-Judaism, these cases were thought to have been lost or destroyed. That's what makes them especially interesting."

Dating from 1593 to 1817, the records in the university's acquisition — one of the Bancroft Library's largest ever — include 61 volumes of original manuscripts. Like the crypto-Jewish trial records, some of the documents were considered missing until they turned up at the California International Antiquarian Book Fair in Los Angeles earlier this year. The documents had been in the hands of a Mexican family since the 19th century.

The yellowing documents, bound in old leather and tied with thongs, include transcripts of many trials of men and women accused of superstition and witchcraft, as well as unacceptable sexual practices.

Priests seducing women in the confessional ranked among the most frequent offenses. Among the less common convictions — a woman who claimed to have sex with saints and a priest accused of profaning the sacraments by officiating at the marriage of two dogs.

Penalties were sometimes severe. An incident of a priest seducing a woman in a choir loft, for example, earned 10 years of exile from Mexico.

However, according to Brem, the Inquisition's bad name has had as much to do with past anti-Catholic propaganda by the British and Dutch as with historical truth.

"The Inquisition [in colonial Mexico] really only prosecuted a very small portion of the population," he said. "Persecution of crypto-Judaism was one of the more dramatic kinds of spectacles because they usually ended in death, especially during the early period of the Inquisition."

Despite such drama, a relatively small number of crypto-Jews were tried by the Mexican Inquisition, says Stanley M. Hordes, an adjunct research professor at the University of New Mexico who has studied the subject.

That fact, he says, suggests many crypto-Jews in colonial Mexico were able to practice their faith in a climate of relative toleration.

The Bancroft Library now owns the largest collection of original Inquisition documents outside Mexico, as well as a rich collection of related historical materials of the period. Its recent acquisition cost "six figures," according to Charles Faulhaber, director of Bancroft Library. The library has mounted a campaign to raise $50,000, the additional funds needed to finance its new acquisition, parts of which are currently undergoing conservation work.

"These are remarkable documents of the material and psychological and intellectual aspects of everyday life," Brem said. "They really do record all aspects of people's lives."

In addition to documents, the collection contains some physical evidence, including finger bones and prayers used for witchcraft.

Also included is a rope that Blas de Magallanes, a suspect accused of not believing in the Holy Virgin, used to commit suicide while in prison awaiting trial. Records show that prison officials found de Magallanes' body when delivering dinner to his cell on August 29, 1597.