Buy a bunch of radioactive substances, collect them from firealarms. Put the radioactive substance in awkward lines, so it resembles some form of writing. Bur

Buy a bunch of radioactive substances, collect them from firealarms. Put the radioactive substance in awkward lines, so it resembles some form of writing. Bury the radioactive substance, wait 1000 years for curious questions of how it got there and what it means.