What are the cylinders in front of the Buddha statue at Nanzō-in Temple, Japan? I recently visited Nanzō-in Temple, Fukuoka Prefecture, Japan, home of a very large bronze reclining Buddha. In front of the statue are many vertical metal cylinders. My initial thought was that they are prayer wheels - and you may tell me that this is the case - but I did not see any obvious means for them to rotate. What are these cylinders?


(image from Wikimedia Commons, licensed CC BY-SA 2.0. Original at https://en.wikipedia.org/wiki/Nanzoin_temple#/media/File:Reclining_Buddha_statues_of_Nanzoin.jpg)
The urns are numbered.

The Many Faces of Fukuoka’s Nanzoin Temple says,


  There are 365 urns in front of the Buddha.  Visitors travel long distances to place messages to their dearly departed loved ones in the urn marked with the day they died.