A British team of archaeologists on expedition in the Peruvian Andes has hailed as "sensational" the discovery of some of the most sacred objects in the Inca civilisation – three "ancestor stones", which were once believed to form a precious link between the heavens and the underworld.

The find, which was made on an isolated Andean mountainside, provoked joy among local specialists and the experts present from, among others, the British Museum, Reading University and Royal Holloway, University of London. No examples of the stones were thought to have survived until now.

"It was a very moving moment," said Dr Colin McEwan, the British Museum's head of the Americas, as he recalled seeing the stones for the first time.

Dr Frank Meddens, research associate of Royal Holloway, who was also on the expedition, said they had "danced a little jig on top of the mountain" after discovering the objects that they had only read about in 16th-century Spanish documents.

The Incas would have been just as overawed. The conical-shaped stones were among the most significant items in Inca society and religion. Key elements in ritual events, they were thought to facilitate a connection between different realms of the world – the celestial and the underworld of the ancestors – with the Inca king, as the divine ruler, acting as intermediary. And they were considered more precious than gold.

"This is a whole new category of object. It is nothing short of sensational," said McEwan of the three stones in red and white Andesite, a hard, granite-like rock, which were excavated some 2.5 metres beneath an Inca stone platform. The platform too was recently excavated and is a structure of distinctive stonework that once symbolised the imperial control of conquered territories.

The site – at Incapirca Waminan – is one of 20 undocumented high-altitude Inca ceremonial platforms explored by the archaeologists around the Ayacucho basin. Such sites were potent imperial symbols of religious and political authority as the Incas expanded outwards from Cuzco, a sacred city of temples and palaces in the central Peruvian Andes.

Ancestor stones represented deities, ancestors and the sun, and were imbued with supreme symbolic significance. They were greeted with incomprehension by Spanish chroniclers of the early 16th century, who sacrilegiously likened their shape to sugar loaves, pineapples and bowling pins. The insult, however, was returned: when the 16th-century Inca ruler Atahualpa was shown a copy of the Bible by the Conquistadors, he reacted with similar contempt.

According to Spanish sources, the stones were used in public solar rituals, sometimes draped in gold cloth and paraded. One witness wrote: "The stones… were held to be blessed and sacred."

Symbols of the ancestral essence of the Inca king, the objects were placed on display when the supreme leader was absent from Cuzco, the capital of the Inca people, in an attempt to demonstrate the perpetual presence and his power. The Incas believed their king to be a living god who ruled by divine right.

As the Incas had no system of writing, the significance of the archaeologists' unprecedented find is reinforced by the identification of ancestor stones in the decoration of a unique 16th-century Inca vessel (cocha) in the British Museum. Spanning 50cm in diameter, it bears a carved scene showing a central solar disc and two kneeling figures with their hands clasped as they honour an ancestor stone. They are flanked on either side by an Inca king and queen and high-ranking lords.

The Incas created a huge empire that stretched more than 2,400 miles along the length of the Andes and whose economy was based on taxed labour, with its people farming and herding animals, working in mines and producing goods such as clothing and pottery.

The sites for ceremonial platforms were chosen for their vistas of the snow-capped peaks, which were worshipped as mountain deities. It was at such sites that the Incas sacrificed children – the ceremony of capacocha – at moments of potential instability.

These structures also had sacred central spaces known as the ushnu, with a vertical opening into "the body of the earth" into which libations such as maize beer were poured. The ushnu platforms served as a stage from which the Inca king and his lords could preside over seasonal festivals and ceremonies.