View photos of the edible plant, Carya tomentosa (Mockernut hickory), profiled in the Wild Edible Series: Alabama, Arkansas, Kansas, Missouri, Louisiana, Oklahoma, and Texas: Vol 1. 

A passage from Wild Edible Plants of Arkansas:

All species of Carya technically have edible nuts, but some species are better tasting than others. Shagbark hickory (Carya ovata) is considered the best tasting; Mockernut hickory (C. tomentosa), good–tasting, but small; Bitternut hickory (C. cordiformis), poor tasting.

A passage from Wild Edible Plants of Oklahoma:

Place the de–hulled nuts in a bucket of water. Discard
the nuts that float (this usually means they’re insect damaged). Remove the submerged nuts and keep them in a dry place.