The lowest common denominator of ¹⁄₆ and ³⁄₁₀ is 30.

It is in this regard that Monsieur Ouine becomes a veritable antipriest, the Pontiff of Hell.

The form I have always recommended is a teaspoonfull of bicarbonate of soda and a tablespoonful of eau de Cologne in a quart (a winebottleful) of water, a little hot water being added, if required, to warm the small quantity poured out for use.

For what it's worth, the vast majority of the fandom picks up on R/Hr over H/Hr.