2) The controversial Replica of Leonardo da Vinci's Adding Machine

On February 13, 1967 an amazing discovery was made by American scientists working in the National Library of Spain, Madrid. They had chanced upon 2 unknown works of Leonardo da Vinci, know as the "Codex Madrid". There was much excitement regarding this discovery and public officials stated that the manuscripts "weren't lost, but just misplaced".

Doctor Roberto Guatelli was a famous world expert of Leonardo da Vinci. He specialized in building working replicas of Leonardo. He had built innumerable such replicas with four assistants, including his stepson Joe Mirabella. In 1951, IBM hired Guatelli to continue building such replicas. They had organiezd a travelling tour of machines, which was displayed at schools, offices, labs, museums and galleries. Dr. Guatelli left IBM in 1961 and set up his own work shop in New York.

In 1967, after the discovery of the "Codex Madrid", Dr. Guatelli flew to the Massachusetts University to study its copy. When seeing the page with the adding machine he remembered seeing a similar drawing in the "Codex Atlanticus". He built the replica in 1968 combining the two drawings.

This replica was shown in the IBM exhibition.
The text beside the replica said:
"Device for Calculation: An early version of today's complicated calculator, Leonardo's mechanism maintains a constant ratio often to one in each of its 13 digit-registering wheels. For each complete revolution of the first handle, the unit wheel is turned slightly to register a new digit ranging from zero to nine. Consistent with the ten to one ratio, the tenth revolution of the first handle causes the unit wheel to complete its first revolution and register zero, which in turn drives the decimal wheel from zero to one. Each additional wheel marking hundreds, thousands, etc., operates on the same ratio. Slight refinements were made on Leonardo's original sketch to give the viewer a clearer picture of how each of the 13 wheels can be independently operated and yet maintain the ten to one ratio. Leonardo's sketch shows weights to demonstrate the equability of the machine."

After a year the controversy regarding the replica had grown and an Academic trial was then held at the Massachusetts University in order to ascertain the reliability of the replica. Amongst others were present Professor I. Bernard Cohen consultant for the IBM collection and Doctor Bern Dibner a leading Leonardo scholar.

The objectors claimed that Leonardo's drawing wasn't a calculator but more of a ratio machine. One revolution of the firstshaft would give rise to 10 revolutions of the second shaft and 10 to the power of 13 at the last shaft. Such a engine couldn't be built due to the enormous amount of friction which would result. It was said that Dr. Roberto Guatelli "has used his own intuition and imagination to go beyond the statements of Leonardo". The vote was a tie, none the less IBM decided to remove the controversial replica from its display.


Roberto Guatelli died in September 1993 at the age 89. Where his famous replica is today is, is unknown. Possibly it is somewhere in one of IBM's storages. The work shop in New York is still own by Joseph Mirabella, with many of the replicas at hand.

1) Biography

3) The Vitruvian Man

4) Quotations by Leonardo da Vinci

5) Sources

6) If you want to know more...