The idea of keeping a human brain alive in a jar (with mechanical attachments allowing sight, hearing, and speech) to enable travel in areas inhospitable to the body might have been inspired by the book The World, the Flesh, and the Devil by J.D. Bernal, which describes and suggests the feasibility of a similar device. The book was published in 1929, just a year before Lovecraft wrote his story.

https://en.wikipedia.org/wiki/The_Whisperer_in_Darkness#Inspiration