Translation of "Once" in English

Le proverbe dit qu'une once de temps vaut une once d'or, mais le proverbe dit aussi qu'une once d'or peut difficilement acheter une once de temps !

There is a proverb that goes "time is money", but there is another one that goes "money can't buy you time".

J'ai rassemblé chaque once de courage en moi

I mustered up every ounce of courage inside me

Il n'y a pas une once de vérité dans ses paroles.

There is not a scrap of truth in his words.

Napoleon expected the Austrians to retreat once more, and that he'd only face a rearguard.

Napoleon expected the Austrians to retreat once more, and that he’d only face a rearguard.