Yoga
If yoga is a feature of your waking life, then dreams of it usually do not have substantial interpretative content -- they are merely replays of normal events. However, if you are not a yoga practitioner in waking life, this dream may indicate a desire for more mind-body balance or harmony with the universe. Or, it could indicate some sort of reference to a convoluted situation in your life.

 

Topaz
Topaz is the crystal of spiritual wisdom and intuition. Often, it is found in dreams of problem-solving concerning interpersonal relationships

 

Hats
Hats as noteworthy objects in dreams are not too common. A hat can be seen as an extension of power and influence in the dream. Removal of the hat by another can be taken as an invitation to confrontation. Giving a hat to another may be considered a romantic wish-fulfillment projection.
Also, the presence of a hat may be related to a dream of percieved balding.

In some cases, the hat is simply a reminder of another event, such as a sporting event involving a professional team, or an activity like skiing or fishing.