The "20g fresh = 2g dry" rule has given me some pretty...intense results. Depending on how they were dried, how old, etc. the potency of dried mushrooms can vary wildly. If you're eating fresh and trying to determine dose based on past dried mushroom experiences, I would start with closer to a 5:1 ratio than an 10:1 ratio by weight to determine dose and work your way up.
True, 10:1 is for cracker-dry mushrooms assuming no significant potency loss during the drying process or storage. If you have dried mushrooms that correspond with 5:1 ratio (I know that is not what you're saying) they were not dried right. Everyone should use desiccant for the final drying step. If with air-drying you have half-potent shrooms then half of it is still water which is pretty bad.
Other than that calculating from dry to fresh should not really be necessary, if you know what type of Psilocybes you have and the far majority is Cubensis then 25-30 grams fresh is a full dose, some even say 35 grams. Actually it should be more dependable since there is no degradation or drying involved if you store fresh ones correctly in the fridge. Be aware of the material of the container they are in. Paper is no good for example. Tupperware or other plastics are better.
The main reason you get wildly varying results with both fresh and dried mushrooms is because they are natural products and the potency is different per batch and even per single mushroom specimen! Unlike well-laid acid blotter which should be more or less consistent. With pills it depends on spreading if they are consistent or not.
A solution to unpredictable intensity is to take a batch of mushrooms of appreciable size and dry them properly till they are cracker dry: first air-drying, then air-tight in a container together with a desiccant present. Then grind the mushrooms up to dust or little chips and mix them, the better you mix them the more homogeneous it should be. And the more homogeneous (or evenly spread) the more predictability you get when measuring on a scale.
To the original question: there is no reason why you cannot make a small portion of tea, it works exactly the same. And there is very little potency loss unless you use too hot water. Do not use boiling water but warm water instead, you could do it in two soaks: first half of the water made warm - steep, then strain the pulp. Add warm water again to the pulp and repeat. By the time you're finished it may be lukewarm but it's better for potency. You can add some lemon juice to the water before you begin to help extraction. And you can add some sugar to make it all more palatable and use a tea-bag for flavor.
Also, lots of people eat the pulp afterwards to be sure. It may defeat the purpose of negating nausea since it seems to me like the fibrous tissue is the stuff that irritates the stomach and not the drugs that go into the tea-water. However, when making tea the fibrous tissue gets rehydrated and may fall apart making it better digestible.
Please visit the psychedelic index:
http://www.bluelight.ru/vb/threads/560442-The-Psychedelic-Index
And browse to the Psilocybin Mushrooms thread. In the first post / OP, there is an index with subthreads including one about mushroom tea.
I encourage you to continue discussion there and also to confirm here that you understand this. I can merge this into that subthread or close.
Have a nice trip when the time is right!
