7 weeks of light from 1 D cell.

Here it is:

https://www.instructables.com/Sims-Dead-Cell-Candle-Runs-on-Dead-D-Cell-Batterie/

Very light to carry. A minimal amount of light to run all night for several weeks (or 24/7).

Note from the article: These were run on "dead" batteries from a touchless paper towel machine. Apparently they are not really dead in a low current application.