A love letter is an expression of love in written form. However delivered, the letter may be anything from a short and simple message of love to a lengthy explanation and description of feelings. One of the oldest references to a love letter dates to Indian mythology of more than 5,000 years ago. Mentioned in the Bhagavatha Purana, book 10, chapter 52, it is addressed by princess Rukmini to King Krishna and carried to him by her Brahmin messenger Sunanda. Examples from Ancient Egypt range from the most formal, and possibly practical – "The royal widow [...] Ankhesenamun wrote a letter to the king of the Hittites, Egypt's old enemy, begging him to send one of his sons to Egypt to marry her" – to the down-to-earth: Let me "bathe in thy presence, that I may let thee see my beauty in my tunic of finest linen, when it is wet". A fine expression of literary skill can be found in Imperial China: when a heroine, faced with an arranged marriage, wrote to her childhood sweetheart, he exclaimed, "What choice talent speaks in her well-chosen words [...] everything breathes the style of a Li T'ai Po. How on earth can anyone want to marry her off to some humdrum clod?" In Ancient Rome, "the tricky construction and reception of the love letter" formed the center of Ovid's Ars Amatoria or Art of Love: "The love letter is situated at the core of Ovidian erotics". Roman Emperor Marcus Aurelius Antoninus and writer of Meditations, exchanged love letters with his tutor, Marcus Cornelius Fronto. The Middle Ages saw the formal development of the Ars dictaminis, including the art of the love letter from opening to close. For salutations, "the scale in love letters is nicely graded from 'To the noble and discreet lady P., adorned with every elegance, greeting' to the lyrical fervors of 'Half of my soul and light of my eyes [...] greeting, and that delight which is beyond all word and deed to express'". The substance similarly "ranges from doubtful equivoque to exquisite and fantastic dreaming", rising to appeals for "the assurance 'that you care for me the way I care for you'".