The Complete Buffet Manual or How to Mix Fancy Drinks by J. E. Sheridan (1901, p.47)

lemonade — plain lemonadebase
0.5 ponyCordial — Added slowly.modifier
  1. Make a plain lemonade and ornament it with fruits in season.
  2. Put in the cordial slowly when called for by the customer and serve.

Garnish: Seasonal fruit.

This is a useful customer-choice service checkpoint because it shows cordial addition as a modifiable finishing act rather than a fixed formula.

The slow final cordial addition is the defining service move.

The Hoffman House Bartender's Guide by Charles S. Mahoney (1905, p.210)

lemonade — plain lemonadebase
fruit — fruit in seasongarnish
0.5 ponyCordial — Put in slowly.modifier
  1. Make a plain lemonade and ornament with fruits in season.
  2. Put in slowly one-half a pony of the cordial.

Garnish: Fruit

The Buffet Blue Book by John H. Considine (1912, p.30)

1 glassplain lemonade base
fruit garnish — fruitgarnish
0.5 ponyCordial — cordial of choicemodifier
  1. Make a plain lemonade and ornament it with fruit.
  2. Pour in about half a pony of the cordial the customer desires and serve.

Garnish: Fruit

The Ideal Bartender by Tom Bullock (1917, p.36) — Bullock 1917

lemonade — Plain Lemonadebase
0.5 jiggerCordial — Any Cordialmodifier
  1. Add half a jigger of the customer's preferred cordial to a plain lemonade.
  2. Serve.

This matters because Bullock explicitly records customer-choice modifier service rather than only fixed formulas.

The open cordial choice is the key historical feature and should remain visible.

Cocktails by Pedro Chicote (1928, p.289) — Cordial

0.5 lemonlemon juice — jugo de medio limonacid
ice — pedacitos de hielobase
water — agua naturaldilution
Seasonal fruit — frutas del tiempogarnish
0.5 vasitocherry cordial — cherry Cordialother
0.5 copitagum syrup — jarabe de gomasweetener
  1. Build in a large glass, stir, and serve with straws.

Garnish: Seasonal fruit

Ice: Ice

This matters because it shows the same lemonade grammar being extended with cordial and fruit in the professional bar.

See also: Lemonade, Orangeade

Source suggests curacoa, creme de menthe, or creme yvette as examples of the cordial choice.