The oldest recipe I know of for a "dry" Martini was brought to my attention by Fernando Catellon. He found it in "American Bar—Boissons Anglaise & Américaines", a French cocktail book published in 1904.
DRY MARTINI COCKTAIL
Verre No. 5
Prendre le verre à mélange no. 1, mettre quelques
morceaux de glace:
3 traits d’angostura ou orange bitter.
Finir avec gin et vermouth sec, quantités égales, remuer, passer
dans le verre no. 5, server avec un zeste de citron, une cerise ou
une olive, au gout du consommateur.
Which tranlates into English as:
DRY MARTINI COCKTAIL
Glass No 5
Using mixing glass No 1, and a few pieces of ice:
3 dashes of angostura or orange bitter.
Finish with gin and dry vermouth, equal quantities, stir well, pour
into glass No 5, serve with a piece of lemon peel, a cherry or an
olive, based on the taste of the consumer.
While using "equal quantities" of gin and dry vermouth might sound rather severe, as long as you use a good fresh vermouth, it is really a delightful libation.