This answer is only from the Theravada viewpoint. It's likely that you can find more diverse meditation techniques in Vajrayana.
Shambhavi Mudra is apparently an eyebrow center gazing gesture.
This source states:
Shambhavi Mudra is an eye-crossing technique which is used as a hack
to activate the parasympathetic nervous system—which is cognate with
There’s a lot of vague opinion here. Several studies have shown at as little as 20 mins (two 10 minute sittings) a day is sufficient to receive benefits. In fact this level of practice is the basis of one of the most popular book-based Mindfulness courses in the world (Mindfulness: A Practical Guide to Finding Peace in a Frantic World).
This book is ...