Approximately 80% of the caffeine in tea is released during the first 30-seconds of steeping, therefore to remove most of the caffeine from any tea simply:
- Pour boiling water over the tea leaves
- Allow the leaves to steep for 30 seconds
- Pour out the brew, saving the steeped leaves
- Re-steep the same leaves with more boiling water for the recommended steeping times.
In another Lifehacker post on caffeine, a comment linked to this guide on the caffeine content in food, drinks and medicines. The chart is much more detailed than the one I linked to in my post on caffeine and headache. The medications list includes some headache drugs.
While I’m on the subject… Pre-Imitrex, a friend treated his migraines by gulping a 12-ounce can of Coke. He didn’t drink caffeine any other time and swore that this was the only treatment he responded to. It didn’t abort the migraine, but lessened it’s severity. Now he takes an Imitrex and drinks a Coke and voilà, migraine aborted completely. With the plethora of caffeinated water on the market, even those with nausea could try it.
P.S. In general I’m suspicious of Wikipedia’s accuracy, but the yerba maté information appears to be correct.