We learn a lot from traditional wisdom – but what would you be able to teach someone from 200 years ago?

As the title says, in gardening, and I think particularly permaculture, there is a lot we can learn from traditional wisdom and practices. However, obviously not everything that was common practice or common knowledge 200 years ago was true. As a species, we have also learned a lot since! If you were given the chance to exchange one bit of gardening/agricultural knowledge with someone from that time, what could you teach them?

(if someone mentions something that people from that time actually DID know, please be kind in your corrections! We can all learn something!)