In S3E3 check Visualise symbol , mostly shown in backgrounds an on t-shirts of visualise members  "A ONE EYE" 

Again in same episode,Bret stiles speaking people , at the minute 10.35 he says 6 dimension (666) symbolism, used also in S6E1 

Again in same episode, Stiles says to Jane ,at 10.42 "Many policeman is visualise member" ,speaking about how he learnt about identification of the member Cecilia's death