Do spanish and french literature beetween 1800 and 1900 ever speak of transhumanism?

Transhumanism is a 20th century idea, so you’re not going to find anything that directly references it prior to the 1920s. That said, you could probably find literature that touches on similar ideas in the era and languages you are looking at. Anything that plays around with the ideas of immortality—especially in a positive way—would relate to the foundational idea of transhumanism, which is to transcend the frailty of our mortal bodies.

I’m not familiar with that term but if “immortality” is an equivalent, I would suggest you search for that term and “French or Spanish literature” in an academic database such as JStor.

Here’s a really good article on the background and current state of transhumanism. It looks like you have to look more to the Enlightenment philosophers and English philosophers such as Roger Bacon for its roots. You may not find a connection to French and Spanish literature per se but it looks like there may be connections to the French philosophes such as Voltaire or Diderot.

@janbb It’s not exactly immortality, though that’s certainly one of the end goals for most transhumanists. The idea is to transcend the mental and physical limitations of humanity (thus “trans-human”) by means of advanced technology. Death is one of those limitations, but so are cognitive biases and easily injured knee ligaments. A useful pre-modern comparison might be alchemy, which also wanted to find both an elixir of life to make us immortal and a panacea to cure all ills (and which used, by its own lights, a scientific approach to discovering these remedies). So I guess we could add alchemical literature to the list.