You get yourself a nice bottle of bourbon* and by the second or third glass you’ve got your water dosage dialed in. Just enough to open it up, not enough to water it down. Well done. Now if like your beverage cold, but don’t want that inexorably melting ice to futz with your ratio, go with frozen soapstone.
This set from London-based Men’s Society gives you six stones in their own cotton storage bag. The volcanic soapstone is non-porous and has a high specific heat capacity — that means it holds its temperature really well, so after an overnight visit to your freezer, it will keep your drink steadily cold for a good long while, never messing with your ratio.