The Rule of 48
All Scientists Are Blind

... some years before [Peter Leavitt] had formulated the Rule of 48. The Rule of 48 was intended as a humorous reminder to scientists, and referred to the massive literature collected in the late 1940s and the 1950s concerning the human chromosome number.
For years it was stated that men had forty-eight chromosomes in their cells; there were pictures to prove it, and any number of careful studies. In 1953, a group of American researchers announced to the world that the human chromosome number was forty-six. Once more, there were pictures to prove it, and studies to confirm it. But these researchers also went back to reexamine the old pictures, and the old studies--and found only forty-six chromosomes not forty-eight.

That is from a neat site HERE.