Shinan Pereira spent a few months in Japan in 1962. Thanks to the wonders of Youtube we can now see the actual instructors he saw give demonstrations and in some cases actually studied with.

Aikido Master Tohei
Sosuishitsu Ryu Jujutsu: Shinan Pereira was a San Moku Roku and originally introduced the Ryu to the United States.

Shinto muso ryu Jo Jutsu: Shinan visited this dojo, but did not train here. He trained in a seminar in Connecticut with Sensei Shimizu during one of his US visits.

Kodokan Judo (Shinan studied with Mifune)
Shorinjiryu karatedo with Shinan Hisataka (Shinan studied briefly in this style)