Boiling is not a correct method to use for making tea, as it extracts the tannin and causes loss of flavour in the steam.
"Ontario Teachers' Manuals: Household Management"
Ministry of Education
I'll draw the tannin out of the whole ounce of you!
"The Rainbow Book Tales of Fun & Fancy"
Mabel Henriette Spielmann
Barebone hoisted the great lug-sail, that smelt of seaweed and tannin.
"The Last Hope"
Henry Seton Merriman