R' Yitzchak of Vienna authored the Ohr Zarua, which was a halachic work of Ashkenazic Jewry. Among his distinguished students was the Maharam of Rothenburg.
An extraordinary story surrounds the preservation of the Ohr Zarua. The only known manuscript copy in the early nineteenth century was lost in a shipwreck. A non-Jewish fisherman later found it off the coast of Holland. Realizing that it was a Hebrew manuscript, he brought it to a local Jew, who in turn passed it on to his Rabbi, R' Avraham Tzvi Hirsch Lehren. The Rabbi's brother, the noted scholar and philanthropist, R' Akiva Lehren, published it in 1862.
Thanks to this remarkable chain of events, one of the great halachic treasures of Ashkenazic Jewry was preserved for future generations.