Apparently I goofed yesterday in referring to the fragment of the lost history of Hesychius. It’s not from the Acts of the Council of Chalcedon, but probably from the Second Council of Constantinople (553 AD), or so a correspondant writes.
Also Mansi is not the latest edition of the material from the councils. This is now Schwartz’s Acta Conciliorum Oecumenicorum. I knew of this series, but had not thought of it as a Mansi replacement. There are no Acta from the first two councils, and the series starts with Ephesus in 433 AD.
I wish this existed in PDF form — what normal person can access it? The editor, Eduard Schwartz, died in 1940. EU copyright is life plus 70 years, which means that the volumes edited by him came out of copyright there in 2010. I am less clear on the US copyright position, tho. Some of the volumes may have appeared before 1923, which would certainly be out of copyright in the US.
The ACO contains a critical text of the documents included, which include literary texts by people like Cyril of Alexandria, for which it is the most recent edition. I was able to find at Fourth Century a list of contents for some early volumes; in a couple of cases complete contents.