The festival of Nemoralia (aka Festival of Torches) was celebrated by the ancient Romans either on the 13-15 August or on the August Full Moon, in honor of the goddess Diana

Diana (mythology)

In Roman mythology, Diana was the goddess of the hunt and moon and birthing, being associated with wild animals and woodland, and having the power to talk to and control animals. She was equated with the Greek goddess Artemis, though she had an independent origin in Italy...

 (see Diana Nemorensis

Diana Nemorensis

Diana Nemorensis, "Diana of Nemi" also known as “Diana of the Wood”, was an Italic form of the goddess who became Hellenised during the fourth century BCE and conflated with Artemis. Her sanctuary was to be found on the northern shore of Lake Nemi beneath the cliffs of the modern city Nemi...

). This festival was later adopted by Catholics as The Feast of the Assumption

Assumption of Mary

According to the belief of Christians of the Roman Catholic Church, Eastern Orthodoxy, Oriental Orthodoxy, and parts of the Anglican Communion and Continuing Anglicanism, the Assumption of Mary was the bodily taking up of the Virgin Mary into Heaven at the end of her life...

.

Ovid

Ovid

Publius Ovidius Naso , known as Ovid in the English-speaking world, was a Roman poet who is best known as the author of the three major collections of erotic poetry: Heroides, Amores, and Ars Amatoria...

 describes the celebration thus:

"In the Arrician valley,
there is a lake surrounded by shady forests,
Held sacred by a religion from the olden times...
On a long fence hang many pieces of woven thread,
and many tablets are placed there
as grateful gifts to the Goddess.
Often does a woman whose prayers Diana answered,
With a wreath of flowers crowning her head,
Walk from Rome carrying a burning torch...
There a stream flows down gurgling from its rocky bed..."

On this day, worshippers would form a shimmering procession of torches and candles around the dark waters of Lake Nemi

Lake Nemi

Lake Nemi is a small circular volcanic lake in the Lazio region of Italy south of Rome, taking its name from Nemi, the largest town in the area, that overlooks it from a height.-Archaeology and history:The lake is most famous for its sunken Roman ships...

 (Nemi, from the Latin nemus, meaning sacred wood or sacred grove), Diana's Mirror. The lights of their candles join the light of the moon, dancing in reflection upon the surface of the water. Today's festival is held in the Greek fashion.

Hundreds join together at the lake, wearing wreaths of flowers. According to Plutarch

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

, part of the ritual (before the procession around the lake) is the washing of hair and dressing it with flowers. It is a day of rest for women and slaves. Hounds are also honored and dressed with blossoms. Travellers between
the north and south banks of the lake are carried in small boats lit by lanterns. Similar lamps were used by Vestal virgins and have been found with images of the Goddess at Nemi.

One 1st century CE Roman poet, Propertius, did not attend the festival, but observed it from the periphery as indicated in these words to his beloved:

"Ah, if you would only walk here in your leisure hours.
But we cannot meet today,
When I see you hurrying in excitement with a burning torch
To the grove of Nemi where you
Bear light in honour of the Goddess Diana."

Requests and offerings to Diana may include: small written messages on ribbons, tied to the altar or to trees; small baked clay or bread statuettes of body parts in need of healing; small clay images of mother and child; tiny sculptures of stags; dance and song; and fruit such as apples.

In addition, offerings of garlic are made to the Goddess of the Dark Moon, Hecate

Hecate

Hecate or Hekate is a chthonic Greco-Roman goddess associated with magic, witchcraft, necromancy, and crossroads.She is attested in poetry as early as Hesiod's Theogony...

, during the festival. Hunting or killing of any beast is forbidden on Nemoralia.