Is that a recipe for gunpowder?

It seems to be missing sulfur, but otherwise - yep.

If memory serves, one of the big reasons for Britain’s naval supremacy for a long time was their discovery and exploitation of large deposits high-quality of saltpeter in India. Before that, they had “saltpeter plantations” with rows of organic waste soaked with human an animal urine and left to dry in the sun. Before that, it was groups of the King’s men going around the countryside and scraping the stone foundations of buildings and cemetery monuments.

My point exactly; people really like to equate "unscientific" with "turned out to be wrong". Chemistry is such a huge field that it's a small miracle we managed to figure out at all, no small thanks to Boyle who actually introduced the very concept of chemical elements.