By removing the C standard lib and using a custom linker you can get the Hello World down to 150 bytes. Here is a fun read: https://hookrace.net/blog/nim-binary-size/.
But that was before 1.0. Updating the example and applying some more tweaks, it’s down to 145: https://github.com/tormol/tiny-rust-executable
actually turns out to be important in embedded work