How to do browser mining without being a jerk?

Context

Of all the ways to make my website (in my case the website runs calculations on the user's games and outputs graphs of it) financially viable, I figured mining would theoretically be one of the least invasive, while still being profitable enough for me. By mining, I mean that there's a script running on the end users' browser, only using cpu power, that mines cryptocurrencies for my wallet.

Question

How to make that process as non threatening as possible for my users?

Should I give them another option? Should I give out rewards associated with it, or on the contrary be as concise as possible about it? Or am I wrong to think it could be a win-win to begin with?