MY LINK ^
In my opinion the most important piece of technology (for animation) is the zoetrope. The Zoetrope was created in 1967 by a man called William George Horner.
The reason that I believe it is one of the most important inventions is because it is one of the first devices to show key movements and also to create a moving image from pictures/ photos. Also we still use a main principle which was used in the Zoetrope which is key movements or as they are known now, Keyframes.