A detail shows what is believed to be Leonardo Da Vinci's thumbprint at A Life in Drawing in London
A detail shows what is believed to be Leonardo Da Vinci's thumbprint (L) on his drawing of The Cardiovascular System and Principal Organs of a Woman, at A Life in Drawing, the largest exhibition of Leonardo's work in more than 65 years, at The Queen's Gallery, Buckingham Palace in London, Britain, May 23, 2019. REUTERS/Dylan Martinez
