A technological advance came with the invention of the “spring-powered clock” around 1500-1510, credited to Peter Henlein of Nuremberg, Germany. Because these clocks could fit on a mantle or shelf they became very popular among the rich. They did have some time-keeping problems, though, as the clock slowed down as the mainspring unwound. The development of the spring-powered clock was the precursor to accurate timekeeping.