Here's one that works without JavaScript, you curmudgeon:
data:text/html;charset=utf-8,%7B%20%22foo%22%3A%20%22bar%22%2C%20%22baz%22%3A%20%5B%20%22qux%22%20%5D%2C%20%22%23render%22%3A%20%22%3Chtml%3E%3Cbody%3E%3Cdiv%20id%3Dcontent%3E%3Ch1%3EMy%20fancy%20document%3C%2Fh1%3E%3Cp%3EThis%20is%20a%20completely%20%26quot%3Bnormal%26quot%3B%20HTML%20document.%3C%2Fp%3E%3C%2Fdiv%3E%3Cstyle%3Ebody%20%7B%20visibility%3A%20hidden%3B%20%7D%20%23content%20%7B%20visibility%3A%20initial%3B%20position%3A%20absolute%3B%20top%3A%200%3B%20%7D%3C%2Fstyle%3E%3C%2Fbody%3E%3C%2Fhtml%3E%22%20%7D
You can paste this directly into your URL bar, and view source to see the valid JSON document.