The first time the Baal Shem Tov was named in a Sefer!!!
Even more interesting that the Author of the Sefer was the Yaavetz, a pillar of the Misnagdim back then!
During the days of the Baal Shem Tov there was a movement called the Frankist. They were promoting anti Judaism ideas and would frequently debate with the Rabbis of the time.
One of these debates took place in the presence of priests in Kaminitz – Podolski. One of the Rabbis chosen to debate was Rabbi Yisrael of Mezhibuzh, the Baal Shem Tov.
Rav Yaakov Emden, knows as the Yaavetz, wrote a small Sefer about this debate called Ma’aseh Nora B’Padolia
and he names the Baal Shem as one of the Rabbi's making this the first time he was mentioned in a Sefer.