Photography as an art is not an exact science. Brassai would time his night exposures with how long it took him to smoke certain cigarettes. – A Gauloise for a certain light, a Boyard if it was darker. Forget the reciprocity charts an experiment.
Brassai's night photos of Paris are amazing; well worth looking at for night photo inspiration. I was just thinking of his interiors shots of people (in bars, clubs) the other day and plan to look at them again soon. All pretty amazing for the time (or any time).
His cigarette technique sounds very practical, though I hate to have to take up smoking just for that.