Simple enough ... locate a previously unknown and undisturbed archaeological site, then introduce an unmistakable anachronism.
Perhaps use a tiny steerable tunneling machine to inject a (suitably aged) BIC biro into the burial chamber of a long barrow, or sneak into an Egyptian tomb a sheet of lead with "I, Nikola Tesla, claim this time and place for Serbia, December 2 1899" scratched onto it.
A "classic" Coca-Cola bottle gripped in the hand of a teracotta soldier, a flintlock musket in the wall of a Roman villa, or a sheet of plastic with "Fifteenth Spatio-Temporal Expedition, Eagle University, Armstrong City, Luna" insinuated into an Mayan pyramid would be equally amusing.-- 8th of 7, Mar 29 2016 Young Earthers expect this http://www.missiont...thousand-years.htmlHow will they know it's a joke? [Sgt Teacup, Mar 30 2016] How long have you been at this? http://www.dailymai...aled-400-years.html [2 fries shy of a happy meal, Mar 30 2016] Oh, I see... http://www.messaget...of-place-artifacts/ [2 fries shy of a happy meal, Mar 30 2016] Even Wikipedia knows about this https://en.wikipedi...t-of-place_artifact [notexactly, Mar 30 2016] Doing this for future generations would be fun. Throw in a pre-rusted broken pile of advanced electronics, with a circuit board with the words ototype ime achin in some strange font would be fun, too.-- RayfordSteele, Mar 29 2016 You do realize this is an evil opposite of "site looting"?-- Vernon, Mar 30 2016 Yes, it's the 'evil' part we like best.-- 8th of 7, Mar 30 2016 Sadly, this is fodder for the Young Earthers (see link), who already expect (and enjoy) the anachronisms you suggest.-- Sgt Teacup, Mar 30 2016 Terry Pratchett's Strata does this, sort of.-- nineteenthly, Mar 31 2016 random, halfbakery