Apparently, there are some historical documents that record that three suns rose in the sky at once some time in 51 AD, and also in 66 AD. In 69 AD, two suns were seen together. According to William Lilly, between the years 1156 and 1648 there were twenty similar occurrences which were recorded.
The following description of this phenomenon appears in a letter written by Jeremiah Shakerley in Lancashire, March 4th, 1648:--"On Monday the 28th of February last, there arose with the Sun two Parelii, on either side one; their distance from him was by estimation, about ten degrees; they continued still of the same distance from the Zenith, or height above the Horizon, that the Sun did; and from the parts averse to the Sun, there seemed to issue out certain bright rays, not unlike those which the Sun sendeth from behind a cloud, but brighter. The parts of these Parelii which were toward the Sun, were of a mixt colour, wherein green and red were most predominant. A little above them was a thin rainbow, scarcely discernible, of a bright colour, with the concave towards the Sun, and the ends thereof seeming to touch the Parelii: Above that, in a clear diaphanous ayr, [air], appeared another conspicuous Rainbow, beautified with divers colours; it was as neer as I could discern to the Zenith; it seemed of something a lesser radius than the other, they being back to back, yet a pretty way between. At or neer the apparent time of the full Moon, they vanished, leaving abundance of terror and amazement in those that saw them. (See William Lilly.)
The Rosacrucians tie this in to their theory of three inner (spiritual) suns.