Here are some news stories, including photos:

http://www.localmemphis.com/news/local-news/civil-war-era-landmine-found-in-arkansas
includes photo

http://www.hotsr.com/news/2016/apr/01/civil-war-land-mine-prompts-evacuation-/
…Bell said the object was 6.25 inches in diameter and weighed 31.6 pounds. He noted he has since learned the Confederate land mines weighed 32 pounds, and speculated that corrosion over the years probably ate away at it, resulting in its reduced weight.
Still thinking it was a cannonball, he said he took it to the Civil War Museum West in Hot Springs. He said he left it in his pickup and brought one of the curators out to look at it. He said the curator told him it was not a cannonball and was in fact a land mine.
"He took me back inside and showed me a photo of one and I realized he was right. I'm really thankful it didn't blow up."
http://www.wkyc.com/news/local/ark-man-finds-landmine-experts-diffuse-danger/115733977
video