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Yoga named your left nostril after the moon, about 600 years ago. Nadi shodhana starts on that side and ends on it.
That small detail is easy to miss. Most people who learn alternate nostril breathing today learn it as a pattern of fingers: thumb on the right, ring finger on the left, swap, repeat. The order feels arbitrary, like a convention someone picked once. It is not arbitrary. It comes out of a map of the body that the hatha yoga manuals took seriously, and this weekend’s full moon is a good excuse to look at it.
Two channels, two lights
The Hatha Yoga Pradipika, compiled in the 15th century, describes the breath moving through channels called nadis. Two of them matter for this practice. Ida runs on the left and is linked with the moon, chandra. Pingala runs on the right and is linked with the sun, surya. Between them sits sushumna, the central channel.
The manual’s instruction for purifying the channels is precise. Breathe in through the left. Breathe out through the right. Breathe in through the right. Breathe out through the left. One round begins on the moon side and finishes there, with the sun side held in the middle.
You do not have to accept the energy map to see the craft in this. A practice that always returns to the same side has a clear end. You know where you are in the round without counting rounds out loud. And the left nostril, in this tradition, is the cooling and settling side, so it is where the manual wants you to finish: winding down, not winding up.
That is a description of the tradition, not a medical claim. Whether one nostril “calms” you more than the other is not something the current evidence settles, and we do not say it does.
Why the full moon
Sharad Purnima is the full moon that closes the monsoon season in the Hindu calendar, celebrated in many places as Kojagiri Purnima. Calendars disagree about whether it falls on the night of 25 or 26 October this year (see, for example, Dekho Panchang’s festival page), so the honest wording is “this weekend’s full moon”.
We are not going to tell you what the festival is for. Families keep it in different ways. What we can say is that a full moon is a natural cue to sit down. It is bright, it is outside your window for a few nights, and it lines up neatly with a practice that the old texts tie to the moon. A reminder in the sky is as good as an alarm on your phone.
A short practice for tonight
Sit upright on a chair or cushion. Feet flat if you are on a chair. Let your shoulders drop.
- Rest your right thumb by your right nostril and your ring finger by your left. Keep the touch light.
- Close the right side. Breathe in slowly through the left for a count of four.
- Close the left side, open the right, and breathe out for a count of eight.
- Breathe in through the right for four.
- Close the right, open the left, and breathe out for eight.
That is one round. You started on the left and finished on the left. Do five to ten rounds, then lower your hand and breathe normally for a minute before you get up.
Keep it soft enough that nobody next to you could hear it. If you feel dizzy or short of air, stop and breathe normally. There is no hold in this version on purpose: it is a gentle evening sitting, not a test.
What the evidence does and does not say
It is worth being plain about the research. A 2025 systematic review and meta-analysis of randomised trials of pranayama for mental health conditions (PMC12392162) found a small evidence base with real methodological limits. Some trials point in a helpful direction for things like anxiety, but the studies are small and varied, and the authors are careful about what can be concluded.
Single sessions of slow breathing tend to produce effects you can feel more reliably than effects a heart-rate monitor can show. Multi-week practice shows more consistent changes in measures like resting heart rate and blood pressure. None of that is about the moon, or about which nostril you finish on. The lunar framing is the tradition’s way of giving the practice a shape. The slow, even count is the part the research actually looks at.
So the case for tonight is modest and practical. A slow exhale that is twice as long as the inhale. Ten quiet minutes. A full moon to remind you.
The count is the practice
The hatha yoga manuals cared about two things here: the order of the sides and the evenness of the count. The order gives you a beginning and an end. The count gives you something steady to follow when your mind wanders, which it will.
A timer helps with the second part. It lets you stop counting in your head and just follow the cue, which is closer to what the old texts were after: attention on the breath, not on arithmetic.
If you want to try it under this weekend’s moon, start on the left, and end on the left.
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