The first flyer in Texas–and his airplane: Slats and Old Soggy No. 1 (2013)

It looks to be a 4-cylinder inline, and if it's a two-stroke engine, I wonder what its intended application was. Certainly not aviation, at that point. (I was going to say that there were no 4-cylinder inline two-stroke motorcycles, but I looked around and found that in 1911 there was at least one company, Pierce, manufacturing them.)

EDIT: now I see that the Pierce was not a two-stroke, despite what I had initially read.

It's pretty early for a 2-stroke; at least according to Wikipedia [0], the first practical two-stroke engine was built in 1908 (though patented around 1880). I'd love to hear more specifics on that aspect if anybody has info.

[0] https://en.wikipedia.org/wiki/Two-stroke_engine#History