Inventions after their time
What inventions or improvements do you know that could have been invented years or decades before they were? The phonograph seems obvious: its components existed at the time moving type was invented. A funnel, a hard wax cylinder, a stylus, and a hand crank, were all the things needed. Instead of 1877 people could have been listening to records in 1677. The telephone itself could have been invented around 1845, at the time of the first practical telegraph. T-stakes instead of wooden fence posts, concrete railway ties instead of wooden ones. How about the little wheels today on our luggage? That could have been done fifty years ago. And Energizer now says they offer a flashlight that accepts three kinds of batteries. It's often not the technology or resources that limits us but the idea.