code: function(evt) {
      if (!this._measureDrag) {
        this._measureDrag = L.circleMarker(evt.latlng, this._symbols.getSymbol('measureDrag')).addTo(
          this._layer
        );
      } else {
        this._measureDrag.setLatLng(evt.latlng);
      }
      this._measureDrag.bringToFront();
    }
docs: mouse move handler while measure in progress adds floating measure marker under cursor