My favorite is any system for writing. That's when we started sending actual information into the future. An argument could be made for art on cave walls, and that does communicate with future humans, but the meaning is interpreted rather than dictated.
Ah, but how did the designer of the first trebuchet have time to perfect their design? Someone else grew extra food for them. How did the farmer produce this surplus bounty? By using the plow!
But you're right, the trebuchet is indeed the superior siege weapon.
I like cement. Roman cement with quicklime. Shit cracks on the limestone flakes which erode and re-calcify within all the micro-fractures. Fuckin Romans were mad smart.