32,883 votes and 556 comments so far on Reddit

Fun fact, the above fact is not in fact, fact
Tracking the history of it the source comes from “Two horses together produced over thirty hp” from this document which was divided by two by Energy Education to come up with 1:15
That document sourced it’s information from Horse: How the Horse Has Shaped Civilizations which said something very different
Edit: For those who may not want to digest the last link here’s a summary of what I see:
A horse, when properly harnessed, can pull overloads of ten or fifteen times [150 lbs out of a hole 220 feet deep in one minute] for short periods, with pairs of horses developing over thirty horsepower
Undefined subject, qualifier, inefficient method “pull” undefined term “overloads” unspecific result [unclear testing method (slope? terrain? shoe? drag from cart?)] undefined period “short”, undefined subjects undefined term “developing” unspecific result indicating multiplicative effect or inaccurate single horse testing
Basically: it’s silliness and shouldn’t be relied on which is why it’s been replaced