Tisha Baav Minhag

The Birkei Yosef [Chida] (O. Ch. 559 : 4) writes:

There were places where the Minhag on Tisha B'av was, to get a person to bend over.

They covered him with a sheet, placed the Sefer Torah on his back and called up the

3 Aliyos.(krias hatorah)

There were Gedolim who tried to abolish this Minhag because,

a) It seems very weird

b) He might pass wind.

The Chida disagrees with them and claims, this Minhag has roots and cannot be abolished.

The Shu"t Dvar Shmuel(249) defends this Minhag even though he doesn't know the source and it seems very strange. 

Possible Source:

In Meseches Sofrim  (18:7) it says, the Minhag on Tisha B’Av is, to wrap

the Sefer Torah  In a black cloth, place it ( Sefer Torah) ** on the floor,

and say Nofloh Ateres Rosheinu. Afterwards you do Kerias Hatorah.

The Abudraham writes , on Tisha B’Av you don’t place the Sefer Torah

in it’s usual place.(Bimah)

It is very possible  this to be the reason for the Minhag .

They didn’t want to put the Sefer Torah on the Bimah or on the floor.

Shuls had no tables so the only place to put down the Sefer Torah

for Leining was on the back of a person.

*"There is no Minhag that looks (weirder) funnier than this".(Teshuva Meiahava O.Ch. 90)

**The Tur & Abudraham’s girsa is Tik Shel S.T.(the Mantel was placed on the floor)