The sheer dimensions of mountains means there are a lot of natural and seasonal elements that could be used as a kigo. The terrain of mountains as seasons change, the localized weather around them, the light and shadow play that goes on throughout the day – especially at sunrise and sunset, the flora and fauna, so on.
snow-capped mountain— wings of sunlight on either side
I remember wanting to write about birds, maybe snow cranes, flying out from behind a mountain peak at sunset. I played with the idea a little before I realized when the sun goes down directly behind a mountain peak, the mountain’s silhouette breaks the sunlight into slanting columns on either side. So I did away with the birds and lent the wings to the mountain itself. On reflection, this haiku has drifted a little further into romanticism than I’d have let it had I been conscious about it when I was writing.