Vervain

Vervain is one of the old-time herbs. The concensus seems to be that it is one of the Verbena species. There seems to be some diversity of opinion on which Verbena it was. Several sources say it was Verbena officinalis.

http://www.sandmountainherbs.com/vervain.html

According to the above link, Vervain is Verbena officinalis. Said to "secure the favour of the ladies."

http://www.herbalextractsplus.com/blue-vervain.cfm?gclid=CPOqmsLJzY4CFREDWAodM1foAw

According to the above link, Blue Vervain is Verbena hastata.

http://www.seedsanctuary.com/herbs/detail.cfm?ID=45

According to the above link, Vervain is Verbena officinalis, and "Historically it has been associated with alchemists and witches, bestowing magical powers to those who use it."