Did Someone Say Proust?

An Ionarts reader recently sent me an interesting and rather esoteric question about Marcel Proust's À la recherche du temps perdu (In search of lost time), a book that occupied a lot of my time last year. With that reader's permission, here was the original message:

I came across your blog in my search for clarification of a reference Proust makes in his novel about "a mythical horse raised by eating nothing but rose petals" or something worded very close to that phrasing. I read all of Proust's novel from 2000 through 2002. I recall some passage that I think was in vol. V, The Captive and The Fugitive, where Proust is making an allusion to something which I don't now recall, but I do remember this reference to the mythical horse that only ate rose petals. I started asking around among those friends who had literature degrees, English degrees, well-read others, but have found no one who can tell me the name of any myth about a horse eating nothing but rose petals. Since your Blog indicates you are recently reading these last few volumes of Proust, I decided to venture this question to you:

Where in the novel is this reference? What is the exact quotation?
What myth is being alluded to and what is the name of the mythical horse so raised?

Finding a single quotation in 7 volumes of 2,500 pages reminded me of the proverbial haystack needle, but the description rang a bell. After a little bit of searching, I located the passage in question, I think. It comes from the last volume—Le temps retrouvé (in English, Time Regained)—which contains, along with the first two volumes, the most beautiful examples of what makes Proust's writing so great. In particular, this passage is found in the last volume's final chapter, An Afternoon Party at the House of the Princesse de Guermantes, in which the narrator recounts meeting all of his friends and acquaintances at a dinner party, after he has been committed to a sanatarium for many years. Seeing them all aged by the years that have gone by, he is struck by the futility of life and confronts his own fear that he will never be able to write the book he wants to write. Here is the translation by Stephen Hudson, who finished what C. K. Scott Moncrieff began:

How would it have profited if, for years longer, I had wasted my nights by letting the words they had just uttered fade into an equally vain echo of my own, for the sake of the sterile pleasure of a social contact which excludes all penetrating thought? Would it not be better I should try to describe the curve, to elicit the law that governed their gestures, their words, their lives, their nature? Unhappily, I should be compelled to fight against that habit of putting myself in another’s place which, though it may favour the conception of a work retards its execution. For, through an excess of politeness it makes us sacrifice to others not merely our pleasure but our duty even though putting oneself in the place of others, duty, whatever form it may take, even, were it helpful, that of remaining at the rear when one can render no service at the front, appears contrary to the truth, to be our pleasure. And far from believing myself unhappy because of a life without friends, without conversation, as some of the greatest have believed, I realised that the force and elation spent in friendship are a sort of false passport to an individual intimacy that leads nowhere and turns us back from a truth to which they might have conducted us. But anyhow, should intervals of repose and social intercourse be necessary to me, I felt that instead of the intellectual conversations which society people believe interesting to writers, light loves with young flowering girls would be the nourishment I might, at the most, allow my imagination, like the famous horse which was fed on nothing but roses. All of a sudden I longed again for what I had dreamed of at Balbec, when I saw Albertine and Andrée disporting themselves with their friends on the sea-shore before I knew them. But alas, those I now so much longed for, I could find no more. The years which had transformed all those I had seen to-day including Gilberte herself must, beyond question, have made of the other survivors as, had she not perished, of Albertine, women very different from the girls I remembered. I suffered at the thought of their attaint for time’s changes do not modify the images in our memory. There is nothing more painful than the contrast between the alteration in beings and the fixity of memory, than the realisation that what our memory keeps green has decayed and that there can be no exterior approach to the beauty within us which causes so great a yearning to see it once more. The intense desire for those girls of long ago which my memory excited, could never be quenched unless I sought its satisfaction in another being as young. I had often suspected that what seems unique in a creature we desire does not belong to that individual. But the passage of time gave me completer proof, since after twenty years I now wanted, instead of the girls I had known, those possessing their youth. Moreover, it is not only the awakening of physical desire that corresponds to no reality because it ignores the passing of time. At times I prayed that, by a miracle, my grandmother and Albertine had, in spite of my reason, survived and would come to me. I believed I saw them, my heart leaped towards them.

I would apologize for the long quotation, but just read it! As for where the story of this "famous horse" comes from, I'm not sure. According to Greek legend, the rose acquired its red color from the blood of Adonis, as he lay dying from wounds inflicted by a boar he was hunting (he should have heeded Venus's warning). Hera's horses were fed on ambrosia, as were those of Apollo's chariot, which drew the sun across the sky (the horses that got out of poor Phaeton's control). I don't know exactly to what Proust was referring in that sentence, however. Any readers have an idea? The original French was "de légères amours avec des jeunes filles en fleurs seraient un aliment choisi que je pourrais à la rigueur permettre à mon imagination semblable au cheval fameux qu'on ne nourrissait que de roses!" I admit that I am baffled so far.

UPDATE:
The same reader informs me that, in response to the same question, Dr. Mark Calkins at TempsPerdu.com responded that the editors of the Pléiade edition of Proust's novel could not identify the myth to which Proust alludes. They surmise that it may be a reference to the story of the golden ass, told by Lucius Apuleius in his complete Latin novel Metamorphoses (translated as The Golden Asse by William Adlington), where the hero, Lucius, is transformed into a donkey and becomes human again after eating a crown of roses. That sounds plausible.