Mania is the energy of Inspiration that fuels the thoughts of any Genius. But it is not generated by geniuses alone. Instead, all kinds of mortal thought can generate low amounts of Mania, with scientific or mathematical thought generating more, and the sort of thought one might call "revolutionary" (politically, scientifically, ethically, it really doesn't matter) generating the most.
Windfalls of mania that occur during revolutionary scientific progression are often very serious events, especially when one of those widely believe theories are discredited. The resulting windfalls of mania often create a Maniac Storm, that spawns new geniuses obsessed with the new scientific paths opened, and Manes and Bardos which appear paradoxically from the theories discredited.
A manweight is the energy equal to the mathematical abilities of twelve random working stiffs according to the Artificers, and it takes one hundred manweight to generate a single mania generated by a Genius can make simply by sleeping.