1900, might have had electric lighting. More likely though would be gas lighting (Gas lights in old homes), the pipe for which was often reused to run electric wires with electric lights replacing the gas. So, you might be looking for holes in the walls, rather than the ceiling that were fixed if that were the case.
gas lighting was not bright you needed multiple fixtures. they could be a ceiling chandler as well as around the room on the walls.
No holes in the wall, or ceiling rose for a central light. Otherwise the original cornicing is still there.
Maybe they just had a really really good plasterer though 