The hехаёmeron was extremely popular in mediaeval Christian literatures. It was a treatise on the Bible story of how God created the sky, the stars, the heavenly bodies, the earth, living creatures, plants and man in six days (hence the name of the book). This treatise turned into a compilation of all the information about animate and inanimate nature that Byzantine scholarship possessed. Of the many hехаёmeron that existed in Byzantine literature, for example, those of John, the Bulgarian Exarch, Severian of Gabala, and later Georgios Pisides were known in Old Russia.
The Нехаёmeron of John, the Bulgarian Exarch, is a compilative work based on the hexaemerons of Basil the Great and Severian of Cabala, but the author also made use of a large number of other sources and added his own reflections. It consists of a prologue and six sections. They tell of the heavenly bodies and the earth, atmospheric phenomena, animals, plants and the nature of man himself. All this information, which sometimes reflects naturalist ideas of the day, and is sometimes obviously fantastic, is imbued with the same idea: admiration for the wisdom of God who has created such a fine, diverse and well ordered world. This idea from the Нехаётеrоп attracted the attention of Vladimir Monomachos who quotes the work in his Instruction and marvels at “how the sky is made, the sun and the moon … and the earth is placed on the waters”, and how diverse are the birds and beasts.
The Нехаёmeron of John, the Bulgarian Exarch, was the most widespread in Russian literature. The oldest of the manuscripts in Soviet libraries is a Serbian one of 1263. Russian manuscripts belong to the fifteenth century and later, but the mention of the Нехаёmeron by Vladimir Monomachos and the existence of fragments from it in a chronographical compilation of the thirteenth century indicate that a translation of the work existed in Russia much earlier.34