Did Dmitri Mendeleyev conjure the organization of elements into the periodic table in a dream?
Among the several places I've seen this suggested is the review of a book (that I haven't read) on Amazon called "Mendeleyev's Dream: The Quest for the Elements", which states:
On the night of February 17, 1869, the Russian scientist Dmitri Mendeleyev went to bed frustrated by a puzzle he had been playing with for years: how the atomic weights of the chemical elements could be grouped in some meaningful way--and one that, with any luck, would open a window onto the hidden structure of nature. He dreamed, as he later recalled, of "a table where all the elements fell into place as required." His intuition that when the elements were listed in order of weight, their properties repeated in regular intervals, gave rise to the Periodic Table of the Elements--which, though much revised since, underlies modern chemistry.
Was this actually a dream that occurred during sleep, as this suggests?