When a good pinch is needed...
As I read some of the more generic herbals, I often see the mention of 1 teaspoonful as a quantity to use for a remedy .
That's fine if you're making a nice cuppa but if you are going medicinal, you'll need more. As you learn your herbs, you'll be able to eyeball the amount you need or even just do it by feel (as each plant and batch have their own unique signature). So in workshops, I recommend at least a tablespoonful of herb for each cup of water.
Me, I work in pinches. A big little pinch for potent herbs like Lobelia and those with a strong flavour or if they're going to be the transport herb in a remedy. A good pinch for most other herbs and a huge pinch for flowers and light herbs like in the pic of Calendula flowers. I'm adding 4 of these to 1 liter of water for a cleansing brew after we've all had colds and our lymphatics are probably clogged full of dead cells and metabolites from the war with our immune systems.
I think a tablespoonful in a cup of water would be alright too. But just as you said, we might even need more depending on how we see it.
It depends a lot on the herb and purpose.
Yes, it is very true.