A hidden figure has been discovered in one of Leonardo da Vinci's notebooks, raising questions about why it was drawn and why it was erased. Experts at the British Library discovered the "fugitive image" using multispectral imaging, which allowed them to view details of the notebook invisible to the naked eye.

Codex Arundel 263 was one of da Vinci's many notebooks – during his career he took more than 7,000 pages of notes. This specific one was collated after his death and pages come from different periods of his life, but with most entries being from 1508.

Topics covered include mechanics, astronomy, architecture and the flight of birds. It shows how most of his ideas and inventions were observed outdoors as he went about his day.

Researchers were particularly interested in one page of the codex because of a small area of discolouration. The page was exposed to light of different wavelengths from ultraviolet to near infrared. Filters were also used to capture images of fluorescence, which generated the image of the fugitive figure on the page – that of what appears to be a man.

da vinci codex
Multispectral imaging showing the figure British Library

"The images raise fascinating questions about why the figure was drawn here, and why great efforts were made to erase it," Christina Duffy, a conservation scientist at the British Library, wrote in a blog post.

However, some have suggested the image could be an indication of da Vinci's jealousy of Michelangelo. The two artists are believed to have strongly disliked each other. Biographer Giorgio Vasari said the pair once had a very public disagreement in Florence during a discussion about Dante. Michelangelo also once described Leonardo's drawings as "no better than my housemaid's".

Martin Kemp, emeritus professor of history of art at Oxford, told the Sunday Times: "It looks like David, but a more muscular one than the statue. "Da Vinci might simply have done this drawing as a reminder and then erased it, because he did not want people to think that he was full of adulation for Michelangelo."

Duffy said more of the pages of the codex will now be scanned in the search for further fugitive images.