While researching another science post, I came across the following image:
The image is from The Harmsworth Monthly Pictorial Magazine, vol. 1 (1898-1899), at the end of the introduction to the magazine by Alfred C. Harmsworth. This seems to be an early version of an LOLcat, popularized by I Can Has Cheezburger! Though I wouldn't exactly call it "laugh out loud", the picture is a captioned image of cats with the caption in the cat's own voice (hence the "we").
I'm wondering if this is the oldest LOLcat found yet -- the oldest one I'm aware of comes from 1905, seven years after the Harmsworth image.
I've said it before, and I'll say it again -- one finds all sorts of interesting things while wandering through old journals and magazines...