Rav Yisroel of Shklov, influenced both by this rush of scientific thought and interested in utilizing a suggestion of the Radvaz of receiving "semikhah" from one of the "Ten Tribes", specifically Reuven and Gad. Rav Yisroel charted out where he thought the Bnei Reuven were probably located, and sent an emissary, Rav Pinchas Baruch, to locate them (Sefer Halikutim to the Shabsei Frankel edition of Rambam, Hilchos Sanhedrin 4:11). Unfortunately, Rav Baruch did not succeed in locating the shevet of Reuven and he was either killed or died while attending to the medical needs of poor Yemenite villagers.