In the Pixar movie Coco, it is stated that you cannot pass to the land of living if your photo is not present at the altar.
I know that Day of the dead tradition is based on real Mexican tradition, where people put photos of their ancestors at the altar as well. But Mexicans probably doesn't believe that there is some algorithm behind that, which would enable dead people to enter the land of the living (according to Wikipedia, sometimes they put things that belonged to the deceased as well).
Of course, one would think that it could substituted by paintings. But what if it is not precise enough. (there is this funny matchmaking machine in the movie) Or the precision is not important?
So, my question is, In-universe, how did dead people cross to the land of the living before photography was invented? Were dead people able to enter the land of living at all?
Maybe the answer could be also connected with the original Mexican tradition, but I don't know it very much, so I am not sure.