Hidden and hidden messages often appear in historical documents -- some credible , others less so . Art diagnostic expert Maurizio Seracini is convinced that da Vinci 's fresco `` The Battle of Anghiari '' lies behind `` The Battle of Marciano . '' Face of the devil recently appeared in a Giotto fresco in a church in Italy . Art historians believe they have found messages in works by Leonardo da Vinci and Michelangelo . Forensic art historians hunting lost Leonardo work based on ` ` clue '' in Vasari fresco , among others .
Hidden and hidden messages often appear in historical documents -- some credible , others less so . Face of the devil recently appeared in a Giotto fresco in a church in Italy . Art historians believe they have found messages in works by Leonardo da Vinci and Michelangelo . Forensic art historians hunting lost Leonardo work based on ` ` clue '' in Vasari fresco , among others .