I used to visit graveyards nearby my village, to look at some of the old stones. The oldest (dated) one I've ever seen was from the 1680s-17xx's, on a road trip during which we stopped at a grave yard in some back country town. Whether it was actually posted in that time, I do not know, and do not speculate to be true, but nonetheless
I know exactly what you mean about looking at gravestones.
About a mile from where I live is a very old church ... St. Mary's, (900 years).
In the grave yard are some gravestones which are barely legible now, but a few of them describe how tough life used to be hundreds of years ago better than any history book.
Folk with large families, and one of a few similar gravestones listing the deaths of all 12 children of a family over a two year period. Plague and pestilence type thing.
Makes you think.
Looking around old graveyards is fascinating, but I have to do it by torchlight, when the suns gone down.