Sleep

Maybe spending days and nights studying literature and doing experiments is their form of recreation. For some people there is no distinction between vocation and avocation.

Many alternate tasks, switching to another problem - this is a rest for them.

From my own experience - I never think “on purpose”, the main thing is to formulate a task. After that, the brain solves it in the "background" and displays options at the most inopportune time (Eureka!).