Many of Watkins early stereoviews were originally issued on glass mounts as well as the more familiar card stock used later. These stereoviews on glass are now very rare.
George Eastman House has an online exhibit of Watkins glass stereoviews. The exhibit includes twenty-one stereoviews from Watkins first excursion to Yosemite in 1861. Also included are two unnumbered views of Black Point, San Francisco.
Shown below are glass views of Yosemite and Mendocino. Click on the thumbnails below to see a high-resolution image.