In an episode of The Twilight Zone, a businessman travels back in time and buys land where he knows oil was later discovered. But he's unable to capitalize on the purchase because the drilling equipment necessary to extract it hasn't been invented yet. Although he knows how to use the equipment, he doesn't have the ability to built it.
Such is a common complaint of time travelers: they know how to use modern technology, but have no idea how to duplicate it in a world that knows nothing of such marvels. So be prepared by keeping this image in your pocket at all times. It'll tell you the basic information you'll need to partially reproduce modern sanitation, medicine, measurement, and chemistry.
What would you add to the poster?
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