If I may, here is a old family recipe for lemon curd which has the non-metric measurements.
Mix in top of double boiler:
2 C white sugar
6 egg yolks
4 egg whites
Juice of 4 large lemons
Grated rind of 3 lemons
3 oz. of butter or margarine ( roughly 3 T)
Stir the mixture until it becomes thick like honey. Place in a large jar or container and place in the fridge.