Around 13000 pages...
In his notebooks
His great imagination and curiosity.
His notebooks aren't necessarily a masterpiece (of literature). Leonardo's notebooks were actual notebooks, meaning that is where he sketched stuff, wrote down his ideas, drew his designs and even made notes about his personal finances. Leonardo's notebooks are a candid record into his life.
Paintings and inventions.
... that he used mirror writing.
About 1587.
In his notebooks
Leonardo de Vinci transcribed his thoughts into notebooks.
His great imagination and curiosity.
In art: Mona Lisa, the Last Supper. His many notebooks, which reported his inventions and scientific studies.
His notebooks aren't necessarily a masterpiece (of literature). Leonardo's notebooks were actual notebooks, meaning that is where he sketched stuff, wrote down his ideas, drew his designs and even made notes about his personal finances. Leonardo's notebooks are a candid record into his life.
Paintings and inventions.
Leonardo wrote a series of notebooks throughout his life, which have been compiled and printed in two volumes.
That he wrote backwards ("mirror writing").
Leonardo's notebooks were inherited by his pupil Francesco Melzi.
Renaissance artists known for keeping notebooks include Leonardo da Vinci, Michelangelo, and Albrecht Dürer. Leonardo's notebooks are particularly famous for their detailed sketches, scientific observations, and artistic theories. Michelangelo's sketches and writings reflect his thoughts on art and architecture. Dürer's notebooks contain insights into his artistic techniques and observations of nature, showcasing the intellectual curiosity of the Renaissance period.
He wrote a treaty on Painting but, Leonardo's writing that is famous wasn't so much a book. His "Notebooks" are his most famous writing.