Put two and two together

What is the origin of the phrase, "put two and two together"?

2 + 2. Do the math.

Or in more figurative terms, take this fact or observation and put it together with another fact or observation, and you'll see what's going on.
SS

There's also the extended version, "put two and two together and make five". Two and two put together of course only make four, so this phrase means "fall into error by drawing more inferences from the available evidence than they will genuinely sustain". (VSD)

"Two plus two equals five" is the way I've normally heard the extended version worded. I also think the "put two and two together" suggests that what you are being asked to conclude is not obscure or difficult. Pamela