CREATE TABLE table_204_850 (id DECIMAL, "name" TEXT, "railway" TEXT, "series" TEXT, "maker" TEXT, "dates" TEXT, "drive" TEXT, "wheel arrangement" TEXT, "weight" TEXT, "power" TEXT, "notes" TEXT)

which locomotive weighs the least ?
SELECT "name" FROM table_204_850 ORDER BY "weight" LIMIT 1
SELECT "name" FROM "table_204_850" ORDER BY "weight" NULLS FIRST LIMIT 1