A thaumaturgist's circle is a little tricky to describe, but I'll give it a shot: One circle inside another circle, approximately one handspan (wrist to tip of middle finger) between them. Between the circles were scribed various runes commonly associated with alchemy and magic. Inside the inner circle was either empty (Thaumaturgist's Circle), or contained an eqilateral triangle (Thaumaturgist's Triangle). If I find any pics online, I'll post ya the links.