Gregor Mendel (1822-1884) was an Austrian monk. He studied math and science at the University of Vienna after becoming a Catholic priest. Then he worked as a high school teacher in a monastery, and tended the monastery garden.
He is most well known for his genetic experiments with pea plants. Mendel cross-pollinated pea plants of different characteristics and recorded the characteristics of their offspring. Through recording the traits of several generations, Mendel came up with Mendel's principles of genetics.
Modern researchers have analyzed Mendel's results and have found that in many cases Mendel's results are improbably accurate (i.e., experimental results are seldom exact in their confirmation of an hypothesis, as Mendel's results appear to be). Rather than accusing Mendel of research fraud, which remains a possibility, some note that this is a case of "confirmation bias" (the expectation of certain results in an experiment leads the researcher to interpret results with that bias, rather than objectively report the results).
Miller, Kenneth, et. al. Biology. Boston: Prentice Hall, 2006.