* Launch a satellite into space powered by a fission reactor with excessive capacity. Plan the trajectory so that in 500 years it crashes back to Earth with an inscribed quartz tablet.
* Commit a terrible crime like JFK assassination or Unibomber and make it your manifesto.
* Genetically modify your children (as an embryo) to contain the relevant information in non-coding regions of their DNA.
* Sneak into a fissile waste containment center and put a marble etching in there.