Censorship in Jewish books is nearly as old as Hebrew printing. Generally, material was censored if it was deemed offensive to the church or anti-government, but other subject matters were occasionally censored too.
This week I acquired a work titled Mesharet Moshe, published in 1858 in Koenigsberg, which today is known as Kaliningrad, Russia. At the time, the city was part of Germany, and was home to many Russian Jews who sought to escape Russian pogroms and anti-Semitism.
This particular copy of the book was heavily censored with tar by a Russian censor (presumably when the book was brought in to Russia). Interestingly, the censored portions displayed here do not concern gentiles or other religions, but rather marital affairs.