We've heard that Isaac Newton developed calculus while in quarantine. It turns out that another calculus pioneer, Leibniz, was also in quarantine, but much later.
In October, 1713, Leibniz was quarantined in Vienna "due to an incident of the plague in the apartment opposite to his" (Gango, 2015).
What did Leibniz do with his time? He wrote letters lobbying to become the Chancellor of Transylvania. He didn't know or care much about Transylvania, but the post would have provided him with a salary and allowed him to live in Vienna. His bid for this post failed and Leibniz had to return to Hanover, where he died in 1716.
Source: Gabor Gango, G. W. Leibniz's Candidature for the Chancellorship of Transylvania, Studia Leibnitiana, 47 (2015): 44-66.