Is there any evidence something like the LDS Endowment was part of Jesus teachings, or part of the belief system of Early Christianity?  The answer is "yes."  The evidence is found in the "Secret Gospel of Mark" which was a longer gospel, written by John Mark, the author of the Gospel of Mark, compiled from the notes and writings of Peter (shortly after Peter had been killed) and the notes notes and writings of Mark.  The "Secret Gospel of Mark" tells of a rich young man who was brought back to life by Jesus, after dying and being placed in a tomb.  Jesus rolled away the stone from the tomb, took the young man's hand, and brought him back to life.  The grateful young man was fascinated by Jesus's teachings.  After being taught by Jesus for six days, Jesus placed a linen garment on the rich young man and "taught him the mysteries of the Kingdom of God" and how to live one's life in a way to get there.  This appears to be very much like the Temple garment, teachings and purpose of the LDS Endowment.