From Manhattan Project: The Untold Story of the Making of the Atomic Bomb by Stephane Groueff, Chapter 42, pg. 274:
…To raise the quality extraordinary measures were taken at the Nash Building to assure conditions of maximum cleanliness during fabrication. In order ro avoid even the slightest presence of organic materials, the girls engaged in the processing not only wore white gloves but were even asked, by embarrassed engineers, when their menstrual periods were due. True or false, the popular belief that women’s hands tend to perspire more during their periods caused concern. The Kellex team could not take the risk of questioning the scientific basis of the legend. Hence charts were prepared on which, next to the name and shift of the girl, there was a column carrying the date of her period. On those days, she would be switched to another job.
I find it extremely curious that testing this hypothesis was something that no one thought could be accomplished and find this anecdote a useful reminder that many conceptual frameworks have meaningful limits at some margin.
Ducks and Economics 