unknown something in or near Eryngium? Pycnanthemum? (Slender Mountainmint P. tenuifolium?)

D&M MD 9/2/11 - so pretty, just can't find it - dagnabit

update 2017-1-31: Maybe something along the lines of Pycnanthemum?
Narrow-leaved Mountain-mint (Pycnanthemum tenuifolium)?
aka Slender Mountainmint
http://www.illinoiswildflowers.info/prairie/plantx/slm_mintx.htm
https://gobotany.newenglandwild.org/species/pycnanthemum/tenuifolium/
https://plants.usda.gov/core/profile?symbol=PYTE&photoID=pyte_002_avp.tif
http://www.marylandbiodiversity.com/viewSpecies.php?species=3743
http://www.kansasnativeplants.com/guide/plant_detail.php?plnt_id=510