The total amount of data from the first spacecraft to perform a Mars flyby was ~600KiB: https://en.wikipedia.org/wiki/Mariner_4#Results
That's tiny, but for interplanetary data transfer in the 1960s it's really impressive.
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I've compiled the parser for my Garden programming language to wasm, so I can offer a web playground: https://www.garden-lang.org/
It's over 600KiB of wasm just for a function that returns a parse error message! I'm not sure if that's a lot (cf JS) or a little (cf typical binaries).