I’m a note to a friend and a national monument, but I fit within an envelope. What am I?

A fall from the heavens in the shade of a tree A lifetime of sun is waiting for me I have a hard shell but break through and you'll see I hold the future of the forest in me

What do you drop when you need it, and pick up when you don’t?

I shave the stubble right off your face, with just a careful, steady pace.

Along with thoughts, I transfer ideas to paper. Shape and size can vary quite a bit, and my price can be cheap, or more than a house. I hold liquid, as we no longer chisel; what is this tool you hold?