There is a field of study, which focuses on the Hekhalot literature. However, the internet gives conflicting information about them.
For example, some state that they were written by the early Tannaim near the first century around the time of the Mishna. Others argue they were written around the year 800 as a response to Islamic influence. Many articles refer to the Rabbis of Israel, other to the Byzantine area, and others to Bavel. The literature as a whole is also often referred to as a group, but not specific book or collection of fragments is explicitly mentioned. (This is akin to talking about the Bible, but never stating which books the bible is composed of)
Where can the texts be found, when were they written, and where (Israel? Bavel? elsewhere?) were they written?