What nut did I find?
That is a buckeye, fruit of Aesculus glabra, also known as the Ohio buckeye tree. The seeds (the "buckeye" part) look sort of like a horse chestnut, but the fruit is different.

Do not eat it!


  The fruits contain tannic acid, and are poisonous to cattle, and humans, as is the foliage. (Wikipedia)


(You can, however, make buckeye candy: peanut butter balls dipped in chocolate.)

This is a buckeye still on the tree, as well as some leaves if you'd like to revisit the source to verify: