By Christian Fraser
BBC News, Rome
Researchers believe early illustrations of how to play the game of chess, found in a long-lost Italian manuscript, may have been drawn by Leonardo da Vinci.
Chess puzzles in the manuscript are very close to today's
Da Vinci was a close friend of Italian mathematician and Franciscan friar Luca Pacioli, who wrote the manuscript.
Pacioli wrote the book - a collection of puzzles called "De ludo scacchorum" found in a private library last year - around the year 1500, experts say.
The puzzles are very similar to those found in daily newspapers today.
So far, three pages of the manuscript have been published, showing carefully drawn diagrams, each representing a possible chess scenario, to which Pacioli offered his solutions - checkmate in a set number of moves.
It was not the first of its kind, but one of the most striking things about it, aside from the practical demonstrations of the game, is the novelty and beauty of its illustrations.
The king, queen, bishop and knight are all represented by elegant and distinctive symbols, coloured in black and red ink; so finely drawn that it soon became clear these must be the hand of another artist.
The researchers say they are confident these are the drawings of Leonardo and they have asked experts in the United States to make a second, independent assessment.
The manuscript was discovered last year among thousands of volumes in a private library in Gorizzia, north-east Italy.
Pacioli and Leonardo were working and collaborating on each other's works around the year 1500.
Leonardo is thought to have understood chess and maybe he even played it.
He made a reference to a technical term from the game in one of his many manuscripts.
This is thought to be the only surviving copy of the De ludo scacchorum.
And if it does indeed contain drawings by the hand of Leonardo, then of course, it will be priceless.