Yeah... I just thought Rin was a bit weird for suggesting that... Though I think I've heard of something similar, but it was done using fireworks so your wishes would come true faster. They say that this way, our wishes reach God faster or something like that... But from the anime Rin suggested to make a time capsule before he went away so I thought that might have been what he meant, though I really wouldn't know for sure since I can't read Japanese. Thanks for the reply~! :)