One afternoon in November 1634, Curzio Inghirami, a young Tuscan nobleman, came across a curious object while tossing stones near a riverbank on his family's estate near Volterra. It looked like a clod, but when Curzio picked it up, it fell apart, revealing a kind of capsule that contained fragments of linen rag paper. On closer inspection, a message in Latin could be seen, an obscure prophecy dating from the Etruscan period. It was attributed to "Prospero, Guardian of the Citadel" and ended with the words: "You have discovered the treasure. Mark the spot, and go away." Curzio, a keen amateur historian, marked the spot, but did not go away. Instead, he began digging, uncovering urns and clay vessels filled with the mysterious capsules known as scarith. Eventually, he would find more than 200 scarith whose story, when pieced together, threw scholars all over Europe into an antiquarian frenzy, vividly recreated by the author, a professor at the American Academy in Rome. Prospero, it seemed, was an Etruscan soothsayer from Fiesole who, in the chaotic days after the Catiline revolt against Rome in 64 B.C., found himself in an unlikely and unenviable position. As vengeful Roman armies descended upon Volterra, in the Etruscan heartland, he was pressed into military service and stationed in a citadel on Scornello, a hill across from the city. There, he gathered together his household gods and sealed his papers in capsules, hoping that they might be discovered in a later, happier time. Foreseeing the day when Etruscan might no longer be understood, he helpfully wrote in Latin as well as his native tongue.

An Etruscan text of any kind would naturally attract attention. But Prospero's texts contained startling information. For one thing, they seemed to suggest that the Etruscan augurs knew more about the coming of Christ than even the Hebrew prophets. "I came to believe in the coming of the Great King, after whom the years shall be numbered," Prospero wrote. He also described Aesar, the deity worshiped by the Etruscans, as having created human beings and endowed them with free will, as the Roman Catholic Church taught. This very point of doctrine was central to the dispute between Calvinists and Catholics, then embroiled in the Thirty Years' War. Elsewhere, Prospero suggested that the Etruscans had been experts in the science of astronomy. For the Grand Duchy of Tuscany, whose prestige increasingly depended on its cultural heritage, the discovery of the scarith ranked as headline news.

There was one little problem. From the very outset, reputable scholars smelled something fishy about Prospero and his scarith, and when Curzio published his findings in a lavishly illustrated book they went on the attack. Etruscans, according to writers like Pliny and Livy, wrote on bolts of linen, not paper. Curzio was unfazed. The scarith, he replied, showed that the "linen books" referred to by the ancients were in fact paper made from linen rags.

He was less successful when the debate over the scarith spread beyond the polite confines of Tuscany, and the finest textual scholars in Europe began picking apart Prospero's Latin. The leader of the wolf pack was Leone Allacci, a Greek librarian at the Vatican, who reveled in the bare-knuckle debating style popular in Rome. "A new Augean stable, full of foul odors and outrage," he wrote, "can scarcely slow my angry charge against ridiculous fables and pure trifles." Warming to his task, Allacci homed in on the Latin anachronisms in the texts and the "plebeian" quality of the writing. Why, he wondered, did Prospero break off his narrative by saying he had run out of paper, when many of the texts were wrapped in paper with no writing on it? "Who is going to believe that paper is what runs out during a siege?" he asked. . He dismissed Prospero as "this fogmaker from Fiesole" and "this Balaam's ass."

Curzio, stung, responded with a defense that ran to more than a thousand pages. Fearful of exposing his Latin to ridicule, he wrote in the Tuscan dialect. But the battle was already lost. Although Allacci had stopped short of accusing Curzio of forgery, the verdict was in. The question was not who done it, but why he did it.

Ms. Rowland skillfully weaves her way through this long-forgotten controversy, framing it within the cultural and political struggles between Rome and Tuscany, and the larger intellectual debates of the period. At every turn she provides fascinating detail about the workings of the scholarly world at a highly sensitive moment, just two years after Galileo (like Pope Urban VIII, a Tuscan) had been forced to recant his theory of the solar system. In a mere 150 pages, not counting endnotes, she summons up a world and an age.

So why did Curzio do it? Apparently, because he did not want to go to law school, which was the family's plan. By forging Etruscan texts, he could look forward to years of happy immersion in the subject he loved the most, history. Ms. Rowland does not discount the Tuscan love of practical jokes, or beffe, so prominent in Boccaccio's "Decameron." How else could one read Prospero's predictions, which often sound like cut-rate Nostradamus: "The vulture hath raised its voice from the face of the Locust. The Locust shall devour Lions. The stones shall sweat in horror." If it was a practical joke, it was a good one. In 1985, which the Italian government declared "The Year of the Etruscans," thieves broke into the Palazzi Inghirami, Curzio's family residence, and made off with the scarith. Fittingly, Curzio had the last laugh.