The urbane 70-year-old Menzies sold more than 1 million copies of his first book, 1421, which argued Chinese sailors mapped the world in the early 1400s shortly before abandoning global seafaring.

His theories are dismissed as nonsense by many academics, but have gained a global following among readers.

"This whole fantasy about Europe discovering the world is just nonsense," Menzies says.

In his latest book, published in the US in June and this month in Britain, he says four ships from the same Chinese expeditions reached Venice, carrying with them world maps, astronomical charts and encyclopedias far in advance of anything available in Europe at the time.

Menzies says Da Vinci's designs for machines can be traced back to this transfer of Chinese knowledge. The great painter and polymath was born in 1452 and is best known for his enigmatic Mona Lisa. But he also left journals filled with intricate engineering and anatomical illustrations.

Menzies says designs for gears, waterwheels and other devices contained in the Chinese encyclopedias reached Da Vinci after being copied and modified by his Italian Renaissance predecessors Taccola and Francesco di Giorgio.

To support his argument, Menzies has published drawings of siege weapons, mills and pumps from a 1313 Chinese agricultural treatise, the Nung Shu, and from other pre-1430 Chinese books, next to apparently similar illustrations by Da Vinci, Di Giorgio and Taccola.

"By comparing Da Vinci's drawings with the Nung Shu we have verified that each element of a machine superbly illustrated by the Italian polymath had been illustrated by the Chinese in a much simpler manual earlier," Menzies writes.

"It's very suggestive, very interesting, but the hard work remains to be done," says Martin Kemp, professor of History of Art at Oxford University and author of books on Da Vinci.

"He (Menzies) says something is a copy just because they look similar," Kemp says. "It's not strong on historical method."

(China Daily via agencies July 30, 2008)