Retired German math teacher Joachim Rittstieg says ancient Dresden Codex and Mayan priests guided him to the legendary Atlantis in eastern Guatemala. A retired German math teacher has spurred a national hubbub in Guatemala by claiming to have discovered an ancient underwater city laden with treasure. Joachim Rittstieg grabbed headlines in March with his visit to Lake Izabal in eastern Guatemala. Buried there, he claims, are eight tons of gold tablets in Plato’s legendary Atlantis. Instead of being dismissed, Mr. Rittstieg has garnered a lot of interest. Guatemalan newspapers called him a “German scientist” and followed his expedition with enthusiasm....