The BSE benchmark Sensex today fell by nearly 85 points in early trade as funds and retail investors booked profits amid a weak trend on other Asian bourses.The 30-share index, which had gained nearly 229 points in the previous two sessions, fell by 84.97 points, or 0.47 per cent, to 17,800.29. Similarly, the wide-based National Stock Exchange index Nifty dipped below 5,400 points level by falling 26.20 points, or 0.48 per cent, to 5,394.80.