Hello Pierre,
In traditional and vintage baking recipes, a standard drinking glass or water glass typically refers to a volume of 250 ml (or occasionally 200 ml depending on the vintage and regional tradition).
Here are the typical measurements for all-purpose flour:
1. In a standard 250 ml glass filled to the brim, you will get approximately 150 to 160 grams of flour.
2. In a 200 ml glass (or a standard faceted glass filled up to the top ring line), you will get about 130 grams of flour.
To ensure your cake turns out with the right texture, avoid scooping the flour directly out of the bag with the glass, as this compresses the flour and adds extra weight. Instead, gently fluff your flour, spoon it into the glass until it mounds over the top, and sweep the excess level with the flat back of a knife.
I hope your family enjoys the cake, and best of luck with your baking today!