Weather charms, known as hos, served as protective devices against bad storms and evil spirits. These charms represented Yalulawei, benevolent water spirits. Prior to a voyage, the power of the Yalulawei would be summoned by the navigator through chanting. It would then be taken along in the canoe to ensure a smooth and safe voyage.
One easy way to draw an illusion is to draw zigg-zaggs on paper. Then look you at the paper in different areas and it will look like the zigg-zaggs are moving.