Tinking about a set of kitchen measures that is metric and... integrated.
One thought: My favourite mug is roughly 400 mL so a "teaspoon" of 10 mL would be quite logical.
If all of my small spoons are identical then they could all be used as measures. No need for separate measures.
Is there such a spoon?
After some quick searching on the web I found a dessert spoon.
Next step is to buy one and try it out. Maybe I can even find a spoon of 50 mL?