O-Sensei derived Aikido mainly from the Daito-ryu Aiki-Jujutsu which he learned from Takeda Sokaku.
Daito-ryu is characterized by ‘early neutralization of attack’ which is basically off balancing from the point of contact, a key element that is ever present in Aikido. The techniques in Aikido all have clear roots in Daito-ryu’s as can be demonstrated in the video below:
The principles are very similar and are directly applicable to Aikido as well though Daito-Ryu’s techniques are not limited to being peaceful hence the ‘harder’ style and is closer to its martial roots. It is hoped that looking through these videos, you learn the principles of the originating techniques to better understand the mechanisms of the Aikido techniques which have been modified to be less about pain but more about throwing the person off balance without too much reliance on pain.