Olfactory
They say that the olfactory senses (the sense of smell) is the sense closest linked to memory. Go on eBay, or to a high-end antiques dealer. Find an item made a good amount of time before you were born that was hermetically sealed, vacuum packed or tightly packaged in some way. Make sure you are in surroundings of completely neutral smell with little or no wind. Open the package. The smell should hearken back to your collective subconscious or memory of a past life. If you are successful in choosing the right item, with the right smell, you will have at least a memory flash, or likely a memory flood of years before you were born. Copyright Statement: Unless explicitly stated, all stories published on Creepypasta.com are the property of (and under copyright to) their respective authors, and may not be narrated or performed under any circumstance.