If there's one thing the internet loves, it's an astonishing optical illusion. That's been proven time and time again - with the infamous 'white and gold' dress, a dog that looks like a clown, and more recently, this photo of an avocado.
The latest to take Twitter by storm is a photo of hiker Patrick Delvernois and his friends celebrating after completing the 2540km Appalachian Trail in the US.
Delvernois shared a photo of his group toasting their success with mini-whiskey bottles. But the photo quickly went viral as viewers realised that there appeared to be only three arms in the photo - but four bottles of whiskey.
The photo was shared on Reddit and subsequently to Twitter by user Jen Gentleman, who captioned it "my brain refuses to believe there are four people in this photo".
The post racked up over 200,000 likes and 40,000 shares from fellow internet users similarly baffled at the shot.
On closer inspection, it becomes clear there are actually four arms in the photo - but one of Delvernois' friends is wearing such an effective camouflage jacket he blends seamlessly into the surroundings.
"This is honestly the first time I’ve ever seen camo print actually do its job," one person wrote.
"This is the first time I've ever seen camouflage worn effectively on the internet and my mind is blown," agreed another.
After the post went viral, Delvernois told Metro he only saw the effect it had "when my friends sent me a screenshot of the Reddit post".
"At the time of the photos being captured, I, as well as my friends, were unaware of the optical illusion that was present."
According to Metro, Delvernois has been walking the trail, which stretches from Springer Mountain in Georgia to mount Katahdin in Maine, in a kilt since last year.