One of the earliest examples of superannuation comes from Roman times. The Roman Empire, recognising the contribution of its military, awarded soldiers pensions for their military service.
This tended not to be in the form of an annual pension that involved gifts of land or one-off payments that were meant to provide security for the soldiers once they had put down their spears (or whatever their weapon of choice might have been).
There could be an argument made for Roman Centurions being the first trustees of SMSFs as they had to manage the farming land they were provided with.
The earliest form of superannuation paid in the US was a pension paid by pilgrims of the Plymouth Colony to an injured soldier. This meant the first pensions paid in the US tended to be disability pensions instead of retirement pensions.
The British pension experience was similar to the US in that they were initially military pensions paid to a chosen few rather than to all who served. Like the US they tended to be paid to military personnel injured during the course of their service.
Even rarer were pensions paid to people who had served their country above and beyond the call of duty. An example of this was the hereditary pension awarded to Admiral Lord Nelson and his descendants in 1806 that was paid until 1951.