Science finally taking on the important questions of our time. Spoiler alert: they say 20% is the max. I say one ice cube should suffice!
https://www.thedailymeal.com/1288559/scientist-weigh-how-much-water-too-much-whiskey/
https://www.thedailymeal.com/1288559/scientist-weigh-how-much-water-too-much-whiskey/