Americano — The Cocktail Ontologist

Variants (2)

The Artistry of Mixing Drinks by Frank Meier (1936, p.70)

1 piece	lemon peel — Lemon peel	acid
1 piece	ice — Ice	base
	Soda water — Soda water	dilution
1 glass	Campari	modifier
1 glass	sweet vermouth — Italian Vermouth	modifier

Build over ice in a tumbler or large wineglass, add lemon peel and a little soda water, stir, and serve.

Garnish: Lemon peel

Ice: Ice

Café Royal Cocktail Book by W. J. Tarling (1937, p.33)

1 slice	lemon — lemon slice	acid
0.25 part	Campari — Campari Bitters	base
	Soda water — syphon water	dilution
0.75 part	sweet vermouth — Martini Sweet Vermouth	modifier

Build the Campari and sweet vermouth in a medium size glass.
Fill with syphon water, add a slice of lemon, and serve without shaking or mixing.

Garnish: Slice of lemon

Source explicitly says not to shake or mix.

See also: Adonis, Amarosa

Do not shake or mix.