慢

I'll focus on the mandala primitive here. I guess Heisig chose this keyword for phonetic reasons and as a character it's the "man" in mandara/mandala (曼荼羅). A mandala is a graphic representation of the universe, here split in 3 planes of existance, the sun representing the cosmos, the eye represents the human observer, the crotch represents the animal instincts.

Source: Kanji Koohii community