Here are some of his pursuits that could be considered hobbies:
* Drawing and painting: Though this was his professional pursuit, it was also a passion he indulged in outside of commissioned works.
* Writing: He kept extensive notebooks filled with observations, ideas, and theories. He even wrote fictional stories and poems.
* Music: He was a skilled musician and played the lyre.
* Anatomy and physiology: He dissected bodies to study human form and function, driven by curiosity rather than medical practice.
* Invention: He designed countless machines, including flying machines, war machines, and hydraulic systems, driven by his desire to understand and manipulate the natural world.
* Nature observation: He meticulously recorded his observations of plants, animals, and the natural world, likely fueled by a deep fascination.
It's important to note that the lines between work and hobby were blurred during his time. He was driven by an insatiable curiosity and an urge to understand the world around him, which led him to pursue various fields.
So, while we might not label them as "hobbies" in the traditional sense, we can appreciate these activities as reflections of his deep intellectual curiosity and his relentless pursuit of knowledge.