The diamond and emerald spectacles were supposed to ward off evil and help the wearer reach enlightenment
An auction in London later this month will sell a pair of rare diamond and emerald spectacles from an unknown Indian princely treasury.
The lenses were fitted in the Mughal-era frames around 1890, according to auction firm Sotheby's.
The eyeglasses will be auctioned for £1.5m-2.5m ($2m-$3.4m) each, said the auction house.
They will be shown for the first time in Hong Kong and London in October, ahead of the sale, reports the BBC.
The technical ability of the cutter and the genius of craftsmanship, as well as the vision of a patron who chose to construct two pairs of eyeglasses unlike anything ever seen before, are all intertwined in these extraordinary curiosities, said Edward Gibbs, chairman of Sotheby's for Middle East and India.
The Mughals, a dynasty that controlled the subcontinent in the 16th and 17th centuries and was noted for its rich artistic and architectural achievements, may have commissioned these spectacles.
A diamond and an emerald were molded into the two spectacles, according to a statement from Sotheby's.
The grade and purity of the jewels are exceptional, and stones of this size would undoubtedly have been the reserve of an emperor, the report added.
The diamond lenses, which were cut as a pair from a single natural diamond, are believed to have come from the Golconda mines in southern India. A single natural Colombian emerald was used to create the teardrop-shaped emeralds.
While regular lenses help vision, these filters were aids for spiritual enlightenment, with diamonds thought to illuminate and emeralds thought to have supernatural powers to heal and ward off evil, according to Sotheby's.
The "most renowned evocation" of such glasses in history and mythology, according to the auction house, can be found in Pliny the Elder's "Natural History," in which the ancient Roman Emperor Nero watches gladiatorial games through the surface of a precious green stone.
Nero's tutor, Seneca, was an expert in light refraction, mirrors, and optics, and those were supposed to be the first-ever spectacles, said the statement.