Yo, check this out:

汝向了 [upside-down 了] 樹枝頭坐禪去時得不

This is from the Léngjiā shīzījì 楞伽師資記, "Record of the Laṅkā[vatāra-sūtra] Masters and Disciples," a sort of proto-koan collection from 8th-Century China. The speaker is Yùquán Shénxiù 玉泉神秀 who is, regrettably, nowadays most famous for losing a poetry contest with Dàjiàn "What is it that's dusty again? Gotcha!" Huìnéng 大鑒惠能. The meaning of the sentence, according to Yanagida Seizan 柳田聖山, editor of the edition I'm reading, is:

Can you sit zazen at the end of a drooping tree branch, or not?

Since I can't, obviously what caught my interest was the word written with 了 followed by an upside-down 了. In Japanese this is pronounced ryōchō and means "droop." Yanagida says that it's in the 五王経, "Five Kings Sutra," but both CBETA and the University of Tokyo's database only seem to have the word with both kanji right-side-up:

T0523_.14.0796b07: ... 腹中了了。亦
T0523_.14.0796b08: 如倒懸。受苦無量。

... The inside of their guts was 了了, and it was as if they were hung upside down, enduring limitless pain.

(Admittedly, that doesn't make any sense if 了了 is supposed to have its usual meaning of "lucid" or "perceptive", so I can totally believe that the second 了 was supposed to be upside down, and was turned the right way up by some stonehearted copyist at a later date.)

Yanagida offers some other places it can be found, including premodern authors noting its oddness, so it certainly seems to exist, but I can't dig up any evidence of it online -- not even of 了鳥, a phonetic substitution that was apparently used by scribes who just could not handle an upside-down character in their books. I suspect that this is one of those quirks of the Chinese writing system that did not make the cut during the Grand Digitization. O tempora! o moji!