Nicholas Roerich made this painting, White Horsemen, with what looks like gouache or tempera, on canvas or board. The palette is so restrained, mostly blues and whites, and he’s scrubbed the paint on thinly, like he’s trying to capture a fleeting moment. Look how the clouds morph into figures; they’re like ghosts, or maybe angels, hovering over this craggy landscape. The paint is applied in such a way that you can almost feel the wind and the chill in the air. The dark blue mountains are solid, but the clouds are all suggestion. Roerich painted a lot of landscapes like this, mystical scenes of the Himalayas. He was interested in the spiritual side of nature, and his paintings remind me a little bit of Hilma af Klint, another artist who was into the occult. They both use simple forms and colours to express complex ideas. And like Klint, Roerich shows us that art isn’t just about what we see, but about what we feel.