There have been numerous attempts to decipher the rongorongo script of Easter Island since its discovery in the late nineteenth century. As with most undeciphered scripts, many of the proposals have been fanciful. Apart from a portion of one tablet which has been shown to deal with a lunar calendar, none of the texts are understood, and even the calendar cannot actually be read.
There are three serious obstacles to decipherment: the small number of remaining texts, comprising only 15,000 legible glyphs; the lack of context in which to interpret the texts, such as illustrations or parallels to texts which can be read; and the fact that the modern Rapanui language is heavily mixed with Tahitian and is unlikely to closely reflect the language of the tablets while the few remaining examples of the old language are heavily restricted in genre and may not correspond well to the tablets either.
Since a proposal by Butinov and Knorozov in the 1950s, the majority of philologists, linguists and cultural historians have taken the line that rongorongo was not true writing but proto-writing, that is, an ideographic- and rebus-based mnemonic device, such as the Dongba script of the Naxi people, which would in all likelihood make it impossible to decipher. This skepticism is justified not only by the failure of the numerous attempts at decipherment, but by the extreme rarity of independent writing systems around the world.