They did have gambling back then. The roulette wheel came about in the 1800's, or they could have shuffled playing cards and drew some out of the deck, or thrown dice.
These aren't "natural" as in "from the earth", but they are trivial ways to calculate random numbers without assistance from a powered machine.
To answer your question though, I'd just flip a coin and calculate a random number in whatever range you want using binary.
These aren't "natural" as in "from the earth", but they are trivial ways to calculate random numbers without assistance from a powered machine.
To answer your question though, I'd just flip a coin and calculate a random number in whatever range you want using binary.