Some of the most important documents for historians of Jewish history are documents that haven’t been saved at all. In fact, they’ve been discarded – into a closed storage space known as a geniza. This custom has its origins in Jewish law, which prohibits Jews from simply throwing away worn out or unneeded texts that contain the Hebrew name of God. To the great benefit of scholarship, Jews have often extended the precept to include all kinds of texts, sacred and profane.

The greatest treasure of this kind is the Cairo geniza, an enormous cache of some 300,000 documents or fragments discovered in 1896 in a synagogue in Old Cairo and brought to the attention of the great Judaica scholar Solomon Schechter. For a thousand years, Cairo Jews deposited texts and documents here that were no longer of use. Aside from the sacred texts – Hebrew Bibles, prayer books, tractates of the Talmud, etc. – there were shopping lists, marriage contracts, divorce deeds, leases, secular poetry, philosophical and medical works, business letters, account books, and private letters. Examining these documents has allowed scholars to paint a vivid and dynamic picture of Jewish society in the medieval Muslim Mediterranean. Today, anyone can go on line and see how scholars have dealt with the mass of material from this geniza, with photographs and translations of examples.

Fast-forward to 2014, when I joined my colleague Jane Gerber of CUNY Graduate Center to study material from another geniza, one that was far less important than the one in Egypt, but that had the attraction of never having been examined. With the indelible image of the two Scottish sisters in mind, we traveled to an abandoned synagogue in the Azores – an archipelago of nine islands in the middle of the Atlantic Ocean, far from the historical centers of Jewish life. The trip was part of an effort organized and financed by the Azorean Heritage Foundation, whose mission is to bring to light the history of the now extinct community of Sahar Asamaim (Sha’ar Ha-Shamayim, or “Gate of Heaven”) that was established in the town of Ponta Delgada in 1821 by a group of Moroccan Jews. The community’s small synagogue, which has lain for years in disrepair, is now being restored, and the geniza materials – filling about 50 large filing boxes – have been recovered and deposited in the Municipal Archives of Ponta Delgada...