William Duane, A military dictionary
“ Whenever the battalion is formed in line and halted, the front directing serjeant or guide, after having placed himself perfectly and squarely in the rank, must instantly cast his eyes down the centre of his body, from the junction of his two heels, and by repeated trials endeavor to, take up and prolong a line perpendicular to himself, and to the battalion; for this purpose he is by no means to begin with looking out for a distant object, but if such by chance should present itself in the prolongation of the line, extending from his own person, he may remark it. ”
