I want to know the answer to the following question:
What Epistle described the cross?
All the background I'm provided with is that "For instance, the Epistle of Barnabas, which was certainly earlier than 135, and may have been of the 1st century AD, the time when the gospel accounts of the death of Jesus were written, likened it to the letter T (the Greek letter tau, which had the numeric value of 300), and to the position assumed by Moses in Exodus 17:11–12.". Is that enough to answer the question?
Answer: yes