This fantasy story by the author of Frankenstein, about a man who drinks a half dose of a potion that bestows immortality, is only borderline mathematical fiction. The only arguably mathematical part comes at the end, sort of the punchline, when the question is asked: if the whole dose makes you live forever, what would half of the dose do? In other words, what is "half the infinite"?
The suggestion for including this story comes from R. Nesvet, who also offers a compelling argument for including it in my database of mathematical fiction:
Contributed by
R. Nesvet
One also must consider the publication context  a late1820s Christmas annual whose target audience was very sheltered middleclass girls and whose usual subject matter was sentimental rubbish. So that one line about 'numbering half the infinite' may have been the *only* math puzzle that many of its readers encountered and were expected to get excited about.

