"Prohibition-era recipe was 1:1:1 with honey, rather than honey syrup, a sickeningly sweet drink by modern standards, no doubt"

What evidence of this other is there other than hearsay from Embury 15 years after Prohibition ended? Boothby 1934 coming right out of Prohibition has it greatly more spirit forward and was closer to the Prohibition era.

Death & Co. adds lavender bitters.

3/4oz + of Honey Syrup

Perhaps we should just call this "Jasmine" if it's the original. That said, I'd definitely "slip" as I poured the Campari. This drink looks pretty tart to me.

I like 1 3/4 oz gin, 3/4 oz cointreau, 1/2 oz campari, 1/4 oz lemon juice with a twist .

I have read that the original recipe calls for 2oz gin 3/4oz lemon 1/2oz triple 1/2 oz Campari. Taste exactly like fresh squeezed ruby red grapefruit juice

Rob Hess's version if this is 4:3:2:1 Gin: Cointreu: Campari: Lemon. It works perfectly in that it's a lovely intro to gin for folks who don't like gin.

Tried the posted recipe and the Robert Hess variation. Greatly prefer the latter. Original recipe lacks complexity. It's all lemon juice. As one person commented, might be better if doubling the Cointreau and Campari in the original recipe.

Went with the more forward version from SE and then added a bit of soda ... for a very hot day. :-)

An excellent drink!  I've been making this with Rye instead of bourbon - Jim Beam's of late.  I also tried a variation using Jim Beam, Amaro Nonino, and (instead of Aperol) an aperitivo I found in Paris when I was (unsuccessfully) looking for a bottle of Select- Poli's "Airone Rosso."  It worked very well. (The Italian shopkeeper in Paris told me that Airone Rosso is very similar to Select.) I also sometimes add 1/8 to 1/4 oz Luxardo maraschino liqueur. And I sometimes substitute Ramazotti for the Nonino. There you have it.

A tasty variation I've seen called the Paper Mache subs cachaca and Averna for the bourbon and Nonino.

Been making it lately with Sfumato Rabarbaro in place of the Nonino. Also very tasty.

Had to sub Meletti, and I drink Rye not Bourbon, still loved it. Looking forward to playing around, maybe trying Cardamaro or Grand Poppy next time. Campari would be too overpowering imo especially if using a stronger flavoured Amaro in place of the Nonino. Lots of opportunity to experiment with this one.

Used 1 oz Woodford,  3/4 lime juice, Averna and aperol:  Very good.  Never tried the original recipe 

Tried with Overproof Bourbon 129 proof... Much better. Less flat than comon proof Bourbon.

After a dear bartender friend recommend Meletti in place of Nonino, we now make them that way. Call it a "Paper Plame", because there's M instead of N. :-)

This is one of those drinks I just don't understand. It is imbalanced, with too much citrus sour overwhelming/even masking the amaro and Aperol's contributions, creating an overly dry, unfulfilling drink. (I don't like the song either, despite my rather eclectic taste in music.) Cutting the lemon way back makes a better drink, although not exciting. I can think of much better things to do with Amaro Nonino.

I looked at the recipe for "Rhubarb and Rye" and wondered: Can Zucca be used in place of Rhubarb bitters? I tried it and the answer is a resounding "NO." Zucca is a Rhubarb liqueur and you would think it would do better than Rhubarb bitters. It doesn't--don't try. The bitters give a smoother and more satisfying taste of Rhubarb.

Also, after trying two variations, I offer two other recommendations: (1) For the over-proof rye, do not use Rittenhouse (at 100 proof) The resulting taste is too harsh, both in the taste and going down. I had a more satisfying outcome with Bulliett Rye (at 90 proof). (2) Finally, I suggest using about one-half of the lemon juice, thus avoiding the possibilitiy of an otherwise too tart drink. Again, start with a small amount of lemon juice (say, 1/4 oz) and add a small amount amount more until you get the amount of lemon juice which is balanced in its tartness with the other ingredients. If you get too much tartness, add a small amount of Aperol until you have the balance you want between tartness and sweetness. Once you get that balance, you'll have a great cocktail!

This is a beautiful hot-weather cocktail. So refreshing. I love when Campari is included to play a supporting role like this. It really only serves to amplify and focus the grapefruit flavors. This is going in my summer rotation, for sure. After I mixed it, I realized I also have yuzu juice, and that might be an excellent variation.

I tried this with Smith & Cross for the Jamaican rum. Bad idea. The sour/leather taste of that rum pushes everything else aside, even bullies like the Lemon Hart, and the high proof makes a strong cocktail downright deadly. Delicious and dangerous with a mellower Jamaican rum, though.