Subject: How could we transmit information to a far distant culture 250Myrs from now

Hi, we geology grad students stumped ourselves. How could we, with only 
modern technology, transmit information across 250myrs (like a time 
capsule) into the future (if, say we were to bury a document under a 
mountain) so that information could be deciphered off what amounts to a 
stone slab... 250 myrs in the future? We built models (yes, we are dorks) 
of the plate tectonics and geochemistry of this future world, but are 
stumped how to transmit information across such vast times. What we want to 
know then, how do engineers think we could preserve precious information 
onto what amounts to a slab of rock, make this slab detectable, say from 
outer space, and then decipherable once it is retrieved? 

Re: How could we transmit information to a far distant culture 250Myrs from now