Related: the uLisp assembler. It's small, elegant, and well-documented.
http://www.ulisp.com/show?2Z88
Also (on the bigger than this rather than smaller), Hoot, Spritely's Guile-on-Wasm project https://spritely.institute/hoot/
Also (on the bigger than this rather than smaller), Hoot, Spritely's Guile-on-Wasm project https://spritely.institute/hoot/