月愛三昧 (Jpn gatsuai-zammai )
The type of meditation Shakyamuni entered to save Ajatashatru, the king of Magadha, from his suffering. Ajatashatru was ill with virulent boils that broke out over his entire body.
These were the effect of his various evil deeds, which included killing his father, Bimbisara, and attempting to kill Shakyamuni Buddha and his disciples.
This story is related in the Nirvana Sutra, which reads:
"Then the World-Honored One, the compassionate and merciful teacher, entered into the moon-loving meditation for the king's sake. Upon entering meditation, he emitted a brilliant ray of light.
This ray of clear coolness fell upon the body of the king, and instantly the boils were healed."
The boundless compassion of the Buddha is compared to moonlight, which illuminates the night, relieving anxiety and bringing peace of mind.