Alan Davidison states one of the earliest recorded versions of the sauce dates back to 1758 "sauce a la hollandoise" from Marin's Dons de Comus. This recipe included butter, flour, bouillon, and herbs; no egg yolks. Davidson also quotes from MeGee (1990) who explains eggs are not needed at all and proper emulsification which can simply be done with butter. He also states that if one does wish to use eggs they are not needed in quantities normally called for in traditional recipes.
sauce aux capres - add drained capers
maltaise - add blood organges
mousseline or chantilly - addition of whipped cream
moutarde - with Dijon mustard