First steam engine being blade turbine design instead of piston. Seems more obvious, wind mills and water wheels were all turbines.
Scientific plant breeding. Gregor Mendel's work remained undiscovered for some fifty years. What if it got attention in 1866 instead of 1920s? For that matter, this was a breakthrough entirely possible centuries earlier.
Lithography instead of movable type printing, actually works better for non-alphabet languages like Chinese.
Optical telegraph, should be pretty obvious once you have telescopes.
Canning, food preservation by heating a sealed bottle, you'd think it would've been invented since antiquity.
Kerosene distillation. The Persian scholar Razi wrote about distilling kerosene from crude oil in the 9th century. Yet a thousand years later we're stilling killing whales for lamp oil.