A prism on the sill

I climbed onto the low cushioned bench beneath the tall living room window. In the pale morning sun lay a small triangular glass prism, left flat beside an empty ceramic mug. I sat on my heels and slowly turned the heavy glass with both palms. A sharp bar of rainbow slid across my denim chest, then stretched along the painted white sill. When I nudged the pointed edge, the colors bent and trembled over the timber grain.