Poetry is a slippery medium. As soon as readers think they have got to the source of meaning, it slips away. The river, elusive and in constant flux, has long been taken as the symbol par excellence of this art form, as in Ovid’s Metamorphoses, where the Maeander, which runs back and forwards in the same motion, stands for the poet’s epic as a whole.

Rivers emerge from springs, which thus stand for the burst of inspiration with which an author sets to their work. The journey towards these sources, the movement upwards towards a higher plane of thought, is often used as a metaphor for the struggle of writing: only when one has drunk of the water will the words at last begin to flow.

These springs, however, do not exist solely in the poetic imagination, and this is where the waters begin to muddy, up here where their course should be clearest. In the ancient world a number of different springs were considered the true source of poetic inspiration, sacred to Apollo and the Muses, those patrons of the poetic class.

At the beginning of his ‘drowned novel’ Danube, the Italian scholar Claudio Magris investigates multiple sources for the titular river, and alights on three: the Breg, the Brigach, or a small gutter trickling out of a lonely house in the Black Forest. Each has their own proponents and detractors, leaving the author to ponder which, if any, is the ‘true’ Danube he is hunting.

The quest for the ‘true’ spring of the Muses is just as elusive, but we can identify three main competitors: Castalia, on the side of Mount Parnassus, Hippocrene on Mount Helicon, and the Pierian spring near the foot of Mount Olympus. Each of the three has their own particular mythology attached, and each their own champions and traditions. And as we trace the course of these poetic springs through history, we find that all three have had their own distinctive influence.

In myth, the spring of Hippocrene was created when the winged horse Pegasus struck a rock on the mountain with his foot, from which water issued. In Hesiod’s Theogony – the earliest catalogue of Greek myth and religion – it is in these waters that the Muses wash, before ‘performing choral dances on highest Helicon.’ Likewise, in his Aetia, the Hellenistic poet Callimachus is transported to Helicon to speak with the Muses, who explain for him the origins of various modern customs. Lower down the mountainside one can still find the Valley of the Muses, an ancient sanctuary where poets and musicians would compete every five years in the Mouseia festivals. The Helicon tradition continued to the modern era: in Keats’ Ode to a Nightingale, it is for a beaker ‘full of the true, the blushful Hippocrene,’ that the poet longs.

Of the other two candidates, one has an equally auspicious set of advocates. Both the Greek lyric poet Sappho, and Petronius, author of the Satyricon, plump for the Pierian spring, which Ovid explained was named after the daughters of a certain King Pierus who sought a contest with the Muses – and promptly lost. In the world of English literature, it was immortalised by Alexander Pope, who warned in his Essay on Criticism: ‘A little learning is a dang’rous thing / Drink deep, or taste not the Pierian spring.’

Last, and perhaps most elusive, is Castalia, the little spring that trickles out of the ravine beside the sanctuary of Apollo at Delphi, the centre of the ancient world. Of all the candidates this has the least established classical tradition, relying on Latin poet Lactantius Placidus’ commentary on Statius’ Thebaid, in which he argues that Castalia was a nymph who was transformed into a fountain to escape the advances of Apollo, who – much like in the case of Daphne – then consecrated its waters for his worship. It was here that pilgrims would purify themselves before seeking the counsel of the Oracle.

Where, then, do the streams that issue from these sources end up? In Ezra Pound’s ‘Hugh Selwyn Mauberley’ they are ‘Pierian roses’ that have been superseded by the sale of ‘half-hose’ on Fleet Street, the symbol of the logical positivism that has led to the spiritual crisis of the West. And at the start of Ray Bradbury’s dystopian novel Fahrenheit 451, his protagonist Guy Montag is warned by his superior about the dangers of reading by directly quoting Pope’s poem.

But it is in the case of Castalia that we find the most extensive – and troubling – afterlife. In Herman Hesse’s The Glass Bead Game, Castalia is the name given to the province of a fictitious central European country populated exclusively by an austere order of monk-scholars, who dedicate their lives to pedagogy and playing the eponymous game. The exact nature of this game is never specified, but it broadly involves the synthesis of disparate intellectual elements: players draw connections between seemingly unrelated concepts, such as classical Indian music and a mathematical formula. It is, in essence, an exercise in intellectualism for its own sake, and Castalia, cut off from the rest of the world, a classic ivory tower. The waters of the fountain have become stagnant, still and undisturbed, any sense of vitality slowly dying.

One fork of this river ends in sterility; another in fiction. In the mid-twentieth century a school of thought emerged claiming that a group of Jacobean poets in the court of James VI of Scotland (later James I of England) were dubbed the ‘Castalian band,’ an argument largely based on a single couplet in one of the king’s own poems. Such claims, however, were later shown to be a fiction by literary scholar Priscilla Bawcutt, who deemed them a myth created to encourage the notion of an established Scottish renaissance.

If one visits Delphi today, one can walk down to the Castalian spring and examine the dry remains of the Roman era fountain built above the archaic site. A few metres further up the road, a narrow trickle of water falls from a spout protruding out of the cliff side, from which tourists can fill their water bottles. We are left with our own version of Magris’ dilemma: which of these should we label the true spring? The quest continues: upwards, ever upwards.