I think there is more then one Holy Grail in perfumery.
Holy Grails are kept at the Osmothèque at Versailles. There is a report of it by Luca Turin in one of his books since he was allowed to take a sniff of the historical Fougère Royale. But normal perfume enthusiasts like us can only test contemporary fougères and guess what the quintessence of it was like.
Personally, I don't think that Houbigant's remake Fougère Royale from 2010 comes particularly close to the original. Fougère was a success story of 19th century perfumery, and a few decades after its launch, many perfume manufacturers had their own Fougère. So, it is a good idea to look for traditional fougères from early 20th century perfumery that are still available.
For reference purposes I recommend ordering a small amount of Fougère
by Harry Lehmann
in Berlin. The manufacture was founded in the 1920's, and they still produce some perfumes according to the traditional formulas. The web site is in German so you might need to use bing or google translator, and it has no shop. Orders are simply accepted via e-mail or phone.
Taking Harry Lehmann's Fougère as a role model for the supposed original helped me to explore the world of those fougères that could be called 'classic' in modern perfumery. It helped me discriminate between the general fougère essence and the specific or individual touch of a fougère. The Holy Grail of classic fougères is somewhere in between the following:Fougère by Harry Lehmann
"Sartorial" by Penhaligon's,"1445"
by Castle Forbes,
"Fougère Royale (2010)"
Some lighter variants are:
"1872 for Men"
And a vetiver with a classic fougère heart:
"Vétiver de Frédéric"