Technically this is a Floridita Daiquiri #3.  Hemmingway took his with no simple syrup and double the rum, hence the name Papa Doble.  

I have adopted this recipe as an official Quickstart Cocktail.

Try adding 1 oz of Mango Puree and a splash of Ginger Liqueur or muddle with a little fresh ginger for a delicious twist.

I use the same rum:lime juice:simple syrup ratio as a daiquiri (2oz:1oz:1/2oz) and (lightly) muddle about eight mint leaves. I use 1 to 1.5 ounces of club soda -- don't want to water it down too much.

Muddle 3-4 ripe raspberries along with standard ingredients for a nice summertime variation.

This version was originally posed by bschneier. It has been adopted as a Quickstart Classic Cocktail.

According to The Gentleman's Companion vol. 2 by Charles H. Baker Jr. (1939)
"Doctors still thought that a lot of yellow jacket malaria cases came from drinking water and swamp mists. The couldn't turn off the swamp water mists but they knew that diluted alcohol was a disinfectant agent against germs. So they put a little rum in their boiled drinking water. This tasted pretty bad so some bright citizen squeezed a lime into the thing, and added a little sugar to modify the acid. Ice made from distilled water took the topical heat off the thing. The 2 originators were my friends Harry E. Stout, now domiciled in Englewood, NJ and a mining engineer associate Mr. Jennings Cox. Time: Summer of 1898. Place: Daiquiri, a village near Santiago and the Bacardi plant, Cuba. Hence the name "Daiquiri."

Morgenthaler says the best recipe (which he got from Diffords) is: 2 1/2 oz aged rum, 3/4 oz fresh lime juice, 1/2 oz simple syrup

I've tried many variations on quantities and either aged, light or dark rum. It really just falls into what your personal preferences are. I like the aged and light rum variations with same ratios but at 2oz, 3/4oz and 1/2 oz. Another example is that Robert Hess calls for this ratio but inverts the simple syrup to 3/4oz and lime to 1/2oz. Whether Difford's is the best recipe, again, is a matter of taste. Cheers.

I have been loving this lately as 2 oz Probitas, 1 oz 1:1 cold process simple, 3/4 lime, which is basically Sasha Petraske spec. Thanks,  Zachary

Zachary. You mean 1 oz lime to 3/4 oz simple, right? Because that's the Petraske spec and the same they use at Attaboy etc today. 

Yeah, sorry - I don't have my book and had it flipped in my head. Thanks,  Zachary

Pretty yellow color. Nice balance, with St. Germain yielding to the herbal Chartreuse and spicy rye. Good acid. An excellent introduction to whiskey. 5 stars.

So that's why they make Angostura in those huge bottles...

A fantastic drink - the orgeat barely holds off the Angostura's bitterness, and opens it up nicely. I can't figure out why the Rye's there, but this is a winner of a counterintuitive drink.

I decided to try this since I have this newly found surplus of homemade orgeat... Absolutely delicious, 5/5. Orgeat finishes cocktails in the same way a nice Picada finishes a Spanish seafood stew.

Fantastic. I need to go buy some some extra bottles of Angostura.

The Trinidad Sour I know and love includes an egg white. Mmm...

The Trinidad sour you know and love is wrong.

Yum! I like it--it's kinda like a vacation in a cold glass.

Also great with lime subbed for lemon and Smith & Cross subbed for Rittenhouse.

Reminds me of a full-bodied falernum which probably makes sense given the lemon and almond notes it should have, this is a 10/10, unbelievable!

This is a classic jaded bartender drink. Not for the general public unless they are open-minded. It's phenomenal! I tried it with bourbon thinking it would soften the bitters but nope! Rye works better and I even upped it to 1oz because why not?

This drink makes me wish I could buy Angostura in liter-sized bottles. Wow. Spice was a bit too dominant for me, but an extra 1/2 oz of pineapple juice balanced it out, taming the spice without over-sweetening.

After much snooping around, and I'm sure more-than-slightly awkward intrusions into the personal lives of Flatiron veterans Damon Dyer, Giuseppe Gonzalez (and even Julie Reiner herself) I found that the actual creator of this masterpiece is in fact ADAM McGEE (aka, the most badass bartender you've never heard of, says Giuseppe). The ratios are forgiving, so tweak them to taste...I especially like that. BTW, fresh unseetened pineapple juice is a must; NO CANS. Also, 2:1 Canella cinnamon works best for the syrup. Make this often... Savor it in a Swizzle, shoot it short, sip it up. Just don't forget to say, "Adam McGee!" (which sorta means !Sláinte! in NYC Tiki-speak).

Thanks. I edited the attribution. And while I'm sure it's *better* with fresh pineapple juice I've made it many times with canned and still really enjoy it.