Thinking about the rushlight story, these would only have been readily available to the poor where there was easy access to animal fat. This could have been a problem when only the elites ate meat on a regular basis. Perhaps we can envisage a scenario where rushes were collected and stripped and the pith ‘wicks’ dipped in melted fat in the autumn, when animals that could not be fed over the winter were slaughtered?
In the 18th and 19th centuries, a range of devices were made for holding rushlights. Unlike wax candles, they don’t drip, so carrying them around was not a problem, but they don’t stand up on their own. The Victorian Web has an interesting little piece by Gertrude Jekyll, the famous English gardener, written in 1904 and it includes some helpful photographs.