Underwater cave within the Sea of Storms in the Past.
Increase the duration of the Pegasus Seed.
"Lengthen Pegasus Seed effect"
The Pegasus Ring is a Magical Ring that Link acquires in Oracle of Ages. There is no possible way to acquire the ring in Oracle of Seasons directly, but it can be acquired by using the Ring Secret.
The ring can be found inside an underwater cave within the Sea of Storms. While in the Past at the south end of the Overworld, Link can find the Sea of Storms surrounded by whirlwinds, preventing him from accessing the center. At the southwest portion of these whirlwinds, Link can dive underwater to find a single space between rocks, in which he can swim to the right and then resurface to find himself now having access to the center part of the Sea of Storms. This portion of the Overworld is not accessible until after Link has completed Jabu-Jabu's Belly and acquired the Zora Scale.
Once inside the Sea of Storms, dive underwater to find a hidden cave. Inside, there is a Treasure Chest which contains the Seed Ring that becomes the Pegasus Ring when appraised.
When equipped, the Pegasus Ring increases the duration of the Pegasus Seeds, allowing Link to run for a longer period of time. This ring is useful for quickly navigating across the Overworld, but it has few practical uses in the game. Even navigating the Overworld has minimal effect as Link can also use Gale Seeds to quickly make his way through the Overworld.