All four of the natural elements are used as reminders - the wind to flutter prayer flags, the fire of a lamp flame from which the rising hot air turns prayer wheels, the rocks on which mantras are carved, and the water of a stream to turn the paddles of a water-driven prayer wheel - so that everything we do, every element of nature, whatever happens to be within our sight, can incite us to inner prayer, to altruistic thoughts.
Prayer flags
When a Tibetan prints those prayers and hangs them up to flutter in the wind, he thinks, 'Wherever the wind passing over these prayers may go, may all living beings there be freed from their suffering and the causes of suffering. May they experience happiness and the causes of happiness.'
Merit
'Merit' is a positive state arising for a while in the mind that helps to counteract negative states of mind. I think that the predominant idea for [Buddhists] is therefore that of purifying the stream of their consciousness by an 'accumulation of merit', to reinforce the positive stream that flows toward wisdom. That's why people do prostrations, walk respectfully around sacred monuments, and make offerings of light in the temples.
Mantra
... 'mantra' means 'what protects the mind' - not from some calamity or other but from getting distracted and from mental confusion. A mantra is a short formula that's repeated numerous times, like the Prayer of the Heart in Orthodox Christianity, which is accompanied by constant repetition of the name of Jesus. Such techniques of repetition are found in all religious traditions.
Reciting helps to calm the superficial movements of the mind and thus to see its underlying nature more clearly.
You use the support of things outside yourself so that everything you see, everything you hear, brings back to mind [an] altruistic attitude and provides material for reflection. Nature itself then becomes a book of teachings. Everything incites us to spiritual practice.
... such customs are far from superstitious. They simply reflect the richness of the means employed by Buddhism to keep on reviving our presence of mind ... [they] are useful outer supports allowing believers to communicate with an inner truth.
[Matthieu Ricard]
The Monk and the Philosopher, p.38-41
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