The diamond is used in many pieces of exquisite jewelry and comes in various sizes. It is, however, in its smallest form that it catches our interest the most: the diamond ring given in token of love and marriage. The actual history of this tradition transcends the perception of its creation as marketing hyperbole. The modern solitaire is just the most recent step on a long road from the past.
Rings date back several millennia, but those that are given as a token of love are first noted by the comic Roman poet Plautus in the 2nd century BCE. In those times, wedding rings were known for their interior inscriptions that recorded the marriage contracts signed in the presence of the Emperor's image. This custom was continued and Christianized by the 4th century, when priests would not permit weddings anymore without the exchange of rings.