Charles Ellicott Commentary Genesis 48:14

"And Israel stretched out his right hand, and laid it upon Ephraim`s head, who was the younger, and his left hand upon Manasseh`s head, guiding his hands wittingly; for Manasseh was the first-born." — Genesis 48:14 (ASV)

Guiding his hands wittingly. —The Septuagint, Syriac, and Vulgate translate, “placing his hands crosswise;” but the Targum of Onkelos favors the translation of our version. There is some amount of philological support for the rendering of the three chief versions; but it must mainly rest upon their own authority, which is, however, very great.