1. The Flush Toilet
Perfected in the late-nineteenth century, this hallmark of civilization has remained largely unchanged since its inception (or, one might surmise, its perfection) in roughly 1880. The basic mechanism inside the tank may be made out of plastic instead of rust-prone metal, but one of the great innovators of the modern toilet, Thomas Crapper, would still recognize the thing and appreciate it for the remarkable piece of engineering it remains to this day. One of the few truly indispensable devices they got right the first time, the immortal porcelain throne has stood the test of time very well, thank you.